# #EndSARS Protest: Discourse and Mobilisation on Twitter

Bello Shehu Bello  Muhammad Abubakar Alhassan  Isa Inuwa-Dutse

###### Abstract

Using the @NGRPresident Twitter handle, the Government of Nigeria issued a
special directive banning Special Anti-Robbery Squad (SARS) with immediate
effect. The SARS is a special police unit under the Nigeria Police Force
tasked with the responsibility of fighting violent crimes. However, the unit
has been accused of waves of human rights abuse across the nation. According
to a report by Amnesty International, between January 2017 and May 2020, 82
cases of police brutality have been committed. This has led to one of the
major protests demanding more measures to be taken. The #EndSARS hashtag was
widely used by the protesters to amplify their messages and reach out to wider
communities on Twitter. In this study, we present a critical analysis of how
the online protest unfolded. Essentially, we examine how the protest evolves
on Twitter, the nature of engagement with the protest themes, the factors
influencing the protest and public perceptions about the online movement. We
found that the mobilisation strategies include direct and indirect engagements
with influential users, sharing direct stories and vicarious experiences.
Also, there is evidence that suggests the deployment of automated accounts to
promote the course of the protest. In terms of participation, over 70% of the
protest is confined within a few states in Nigeria, and the diaspora
communities also lent their voices to the movement. The most active users are
not those with high followership, and the majority of the protesters utilised
mobile devices, accounting for 88% to mobilise and report on the protest.
Moreover, we have examined how social media users interact with the #EndSARS
movement and the response from the wider online communities. Needless to say,
the themes in the online discourse are mostly about ending SARS and vicarious
experiences with the police, however, there are topics around police reform
and demand for regime change. We surmise that injecting a political undertone
could lead to setbacks in social activism as it will likely provoke counter
protest.

###### keywords:

Online Activism, Online Protest, EndSARS Protest, Online Social Networks,
Twitter

##  1 Introduction

On October 11, 2020, a special directive banning Special Anti-Robbery Squad
(SARS) was issued via the Twitter
handle111https://twitter.com/NGRPresident/status/1315273093221318656 of the
Presidency Nigeria (see Figure 9(d)). The SARS is a special police unit under
the Nigeria Police Force, responsible for fighting violent crimes such as
robbery and kidnapping. The unit has been accused of various atrocities and
human rights abuse including torture and murder across the nation. In a report
compiled by Amnesty International, there are various cases of torture, ill-
treatment extortion, and extrajudicial executions carried out by officers of
the SARS [1]. According to the report, between January 2017 and May 2020, 82
cases of police brutality have been committed. The tipping point of the
protest is attributed to the period when a video of a man being killed went
viral. This and confounding allegations of police brutality led to an intense
spate of protests against the activities of SARS. Despite the Presidential
directive, the protest continues because the protesters view the details of
the disbandment to be insufficient. The dissatisfaction led to intense
protests demanding reforms beyond SARS, but the Nigeria Police Force. As a
result, there were many incidences of clashes between the police and
protesters. The infamous Lekki bridge has been widely reported, especially
online. Prior to these events, the protest has been ongoing on Twitter for a
very long time. We were able to trace one of the earliest tweets about the
movement (see Figure 9(a)), and the hashtag #EndSARS appears to be the
trademark of the online protest to draw attention to human rights violations
labelled against the SARS police unit. Many studies analysing the attitudes of
the public towards the police have been published in the past [2, 3, 4, 5, 6].
Most of these studies preceded modern social networks such as
Twitter222https://twitter.com/ and Facebook333https://facebook.com/. With the
arrival of online social networks, among other things, citizens are empowered
to express and report their experiences with law enforcement officers. An
earlier study reported how vicarious experiences result in negative
perceptions about the police [4]. With online social networks, rich
information about primary and secondary encounters with the police can be
easily retrieved. This makes it easier to track public attitudes towards the
activities of the police. Public dissatisfaction and demand for social justice
often result in social movements with the potential of bringing drastic social
reforms [7]. Online platforms facilitate social activism that attracts the
attention of diverse individuals. A case in point is the #BlackLivesMatter
online movement [8, 9, 10, 11] and the #EndSARS protest [12, 13, 14, 15, 16,
17, 18, 19]. While discourse about #EndSARS has been ongoing on Twitter, it
was the early October 2020 incidence of the police shooting that triggered
public anger leading to the protest [20]. Of interest to this study is to
explore the following aspects in relation to the online protest:

  1. 1.

How does the protest escalate and how engaging is the protest theme? In this
question, we are interested in studying activity trends during the #EndSARS
movement.

  2. 2.

Who are the key online players during the #EndSARS protest? This question is
geared towards identifying and characterising the influential stakeholders
during the protest. Essentially, we are interested in determining whether the
promoters of the protest reside within or outside the country (the diaspora
community). It has been reported that the diaspora community is a strong
player in this kind of movement [21, 15]. This study will focus on a different
approach to offer a high-level categorisation of the users based on devices
used to tweet about the protest and the location information.

  3. 3.

Is the online protest purely about #EndSARS? This is crucial because, at some
point, the protest has transformed from opposition to police brutality to a
movement for social justice and government reforms.

  4. 4.

What are the main themes in the protest and public perception about the
movement? The goal of this question is to identify topical themes in the
protest and how the online public responds to the protest.

The remaining part of the paper is structured as follows. Section 2 presents
some related work and Section 3 offers a detailed description of the data
collection and preliminary analysis. Section 4 offers the results and
discussion and Section 5 concludes the study and discusses some future work.

##  2 Related work

In this section, we provide some related studies within the areas of public
attitudes towards police [2, 3, 4, 5, 6], social activism [22, 23, 24, 7, 25,
8, 9, 11], and the #EndSARS movement [12, 13, 14, 15, 16, 17, 18, 19].

###  2.1 Public Attitudes Towards Police

There is mixed reaction and perception about the relationship between police
and the public. The attitudes of citizens towards the police have been
investigated long before online social media platforms. For instance, the work
of [2] is focused on the satisfaction of the citizens towards the role of
police in precipitating civil disorder. Many factors have been attributed to
the tense relationship between police and the public. In the USA, race is
considered to be one of the most salient predictors of attitudes towards the
police with African Americans expressing more dissatisfaction than Whites [4].
Using survey data, the work of [3] examines the public perceptions of
misconduct, such as verbal abuse, excessive force, unwarranted stops, and
corruption, involving police in the United States [26]. In lower-class and
high-crime communities, police officers were more likely to be verbally and
physically abusive towards citizens [5]. In another study, citizens who
initiate disrespect towards the police were more likely to be treated
disrespectfully by the police officer [6]. Vicarious experiences also result
in negative perceptions about the police [4]. This could be a key player
during the #EndSARS protest since some of the protesters are angry because
they have an indirect negative encounter with police brutality. Online social
media platforms make it easier to track public perception or satisfaction with
the activities of police and mobilise for social activism.

###  2.2 Social Activism

Social movements have been influential in framing and shaping social discourse
by making it clearer for the affected individuals or communities to understand
societal issues in a specific way [22, 23]. The quest for social movements
have resulted in various societal reforms. For instance, the popular March on
Washington for jobs and freedom advocating for the civil and economic rights
of African-Americans [7]. With the growing interconnectivity, social activism
is becoming widespread on various online social media platforms. The
challenges affecting marginalised communities and movements can be brought to
the limelight by leveraging online social media platforms. Through the Twitter
platform, the #BlackLivesMatter movement has resulted in effecting change and
injecting uniquely black concerns and perspectives into the national discourse
[25]. Past studies have explored various dimensions and impact of the
#BlackLivesMatter (or BLM) online movement [8, 9, 10, 11]. In the work of [8],
the focus is on how social media users interact with the BLM movement and how
online communities influence the framing of the movement. The authors found
that the discourse is centred around solidarity or counter-movement sentiments
towards the movement. The manifestation of the movement on Twitter has been
studied in [11]. The BLM movement has been used by daters use to explain their
responses to social justice movements around race and racism in the United
States [9]. Online activism tends to be effective via social media platforms
because of the rate at which a large audience gets to be aware of the issue.

####  2.2.1 Online Social Networks

The Internet has been instrumental for research involving minority voices
[27]. By enabling interconnectivity among various devices, the Internet is one
of the inventions that change the world [28]. The advancement in digital
social networks has provided the opportunity for huge datasets to be used to
examine the actions and behaviour of users at different levels. Access to
online services or the Internet via smartphones and other digital devices
makes it possible to present and amplify societal challenges that will rather
go unnoticed. Data from social media platforms are quite popular for various
research across domains [29, 30]. With social media, the breadth of available
data sources has expanded rapidly, making it possible to add more value to the
traditional modes of generating and utilising research data. The suitability
and relevance of data from Twitter have been assessed for biases inherent in
social media usage in social research [31]. Today, a large proportion of the
populace relies on social media for various purposes. For instance, according
to [32], around 7 out of 10 Americans use social media to connect, engage with
news content, share information and entertain themselves. While young adults
were among the earliest adopters, the social media user base is growing more
representative of the broader population [32]. Social networking sites gain
the highest number of users around the world in which they provide their
information, thoughts and opinions through various means, such as mobile
phones, laptops, and tablets [33]. Social media platforms such as Twitter
permit instantaneous conversation and participation at any time making them
suitable for bringing societal issues to the surface. Such platforms have been
instrumental in reshaping social discourse and movements by attracting diverse
individuals to engage in direct or indirect communication. For research
purposes, Twitter is useful in both organising and protesting. Users engage
using various means - posting (tweeting), reposting or sharing (retweeting),
liking, etc. A hashtag or group of hashtags are used to denote a topical
discourse on Twitter. Such discourse may emanate from individuals or
communities of users interested in promoting or expressing dissatisfaction.
Similar to the #ENDSARS protest, hashtags have been used to speak out against
the activities of the police handling the SARS initiative.

###  2.3 #EndSARS-related Studies

As noted earlier, in early October 2020, a video surfaced on social media of
police officers struggling and the subsequent shooting of a young man. This
incidence was identified to involve the SARS unit of the Nigeria Police
Force444https://www.npf.gov.ng/aboutus/History_Nigeria_Police.php and
triggered a heightened spate of the #EndSARS protest [20]. Since the incident,
many studies have been published around the protest theme [12, 13, 14, 15, 16,
17, 18, 19]. The circumstances that led to the emergence of the #EndSARS
protest, and the impact of the mass action on policing and law enforcement in
Nigeria have been examined in [34]. While the focus in [35] is on how the
protest affects the Nigerian economy, the work of [18] is geared towards
ascertaining the reasons behind the #EndSARS protest in the hope of proffering
some useful solutions. From the legal point of view, the work of [17] examines
how the police action (SARS unit) implicates Nigeria and the impact on
democracy concerning civil and human rights. The study points to the lack of
mutual trust between the government and the citizens. For online activism,
Nigerians in the diaspora have played a crucial role in influencing social
reforms [21]. This is in line with recent findings [15, 36]. The online
activities and characterisation of the protest have been examined to
understand how the movement is promoted. The strategies used by the protesters
include calling-out celebrities, unfollowing political leaders, sharing
stories, fundraising and hacktivism [36]. Also, the role of influencers within
the movement has been analysed in a related study. It was found that users
relied more on foreign media than local media for coverage while Nigerians in
the diaspora promote information propagation about the protest [15]. The top
10 influencers are scored based on the connection of each user to disconnected
users within the network structure [15]. This construct results in Nigeria’s
president and Lagos state governor (and other media houses) being ranked high
on the list. We focus on a different approach to identifying top influencers
based on their online activity vis-a-vis the protest.

##  3 Methodology

To answer the questions raised in Section 1, our approach is centred around
the following (1) collecting #EndSARS-related data from Twitter (2) performing
a preliminary analysis of the data (3) identifying relevant stakeholders,
performing trend, discourse and engagement analyses. We describe these
processes in this section.

###  3.1 Data Collection

This study utilises data from Twitter, which offers an essential mixture of
diverse user groups that are suitable for research purposes. Through the
platform’s application programming interface (API), we developed a Python
application to retrieve relevant tweets based on the terms in Table 1 for
analysis. A tweet object is a complex data object consisting of many
descriptive fields that enables the extraction of various features related to
a post on Twitter. With the aid of the API, numerous fields can be pulled out
from the tweet object. Accordingly, we leverage the API to retrieve both
historical and live tweets related to the #EndSARS protest from 2017 to 2021.
Table 1 shows a summary of the terms used for collection. In line with
Twitter’s regulation555https://developer.twitter.com/en/developer-
terms/display-requirements, we ensured that best practices have been followed
in collecting and using the data for our research purposes. Table 2 shows
basic statistics about the collected data.

Table 1: Hashtags used in collecting the research data from Twitter Tweets |  based on keywords and hashtags related to the protest
---|---
Description |  collection of #EndSARS-related tweets via Twitter’s API
Hashtags |  #EndSARS (using a variation of the hashtag), police brutality, stop the killing, Nigeria Police, SARS Nigeria, Lekki bridge,#endpolicebrutality

###  3.2 Preliminary Analysis

Because the data collection was conducted over time, we performed some
longitudinal and exploratory analyses to explore the data.

Table 2: A summary of basic statistics in the collected datasets. |  Data Kind | Size | Mean Values | Description
---|---|---|---|---
Dataset |  Raw Tweets | 3550 | 23 | average number of tokens in the tweet
Retweeted Tweets | 3422 | 463 | average retweet count
Replied Tweets | 1317 | 0.3 | average replies in the collection
Quoted Tweets | 1107 | 0.14 | average number of quoted tweets

####  3.2.1 Activity Trend

The collection period covers 2017-2021, which corresponds to the period when
discussion about the protest theme started. In Figure 9, sub-figure 9(a)
appeared to be one of the earliest tweets to bring the SARS issue for open
discussion on Twitter. During the early days of the protest, there were a
handful of users discussing the issue. However, as the issue is debated over
time, the engagement flared up, especially during the height of the protest
(2020 - 2021), which coincides with a period when a video about a police
shooting went viral on social media platforms. Figure 1 depicts how the online
discourse on #EndSARS varies over time. Sub-figures 1(a) to 1(d) depict the
rate of tweet generation over time. The spike in sub-figure 1(a) coincides
with the shooting incident alluded to earlier (see Figure 12). Sometime in
2020, news about the alleged killing by SARS officers was shared on social
media platforms, and the incidence is attributed to the observed peak in
Figure 1(b). However, the veracity of the information was denied by the
Government and the individual responsible was apprehended. Moreover, the
spikes in activity in Figure 1(a) can be attributed to self-reported
encounters with the police or related traumatic experiences with the SARS
officers. As time passed by, the protest recorded low online participation
between January to August 2021. As shown in Figure 1(d), towards the end of
the same year numerous protesters increased tweeting in memory of the October
2020 incident and protest-related themes.

(a) 2012 - 2019 Period

(b) January to June 2020

(c) July to December 2020

(d) Year 2021

Figure 1: Frequency of tweets related to the protest from 2017-2022 showing
(a) the beginning of the protest discussion on Twitter covering 2012-2019; the
spike in activity can be observed towards the end of 2017 (b) tweets about the
#EndSARS protest that were generated in 2020; and (c) tweets about the
#EndSARS protest covering 2021 to early 2022. The sub-figure (d) shows the
devices mostly used by the users discussing the protest themes on Twitter.

##### Offline Protest

The #EndSARS protest happened concurrently both in offline and online modes.
From Figure 1 it can be observed that since the first mention of the protest
theme in 2017, the activity trend has been decreasing until late 2020 when the
tragic shooting incident involving SARS officers that led to the loss of life
666https://www.aljazeera.com/news/2020/10/22/timeline-on-nigeria-unrest
happened. This led to a wider protest across the country. Figure 2 depicts the
proportion of the #EndSARS protest according to the 36 states in Nigeria,
including the Federal Capital Territory (FCT) Abuja. It can be observed from
the Figure that the most active promoters of the online protest are confined
to a few locations, notably Lagos and Abuja. As the protest keeps raging, it
draws the attention of various national and international stakeholders.
Thousands of Nigerians across the nation, especially in Lagos and Abuja,
poured onto the streets protesting over the activities of the SARS unit. This
led to another encounter with the police leading to some organisations
expressing concerns over the handling of the incident. For instance, Amnesty
International (AI-Nigeria) cautioned the authorities over the handling of the
incidence (see sub-figure 9(c)). Moreover, both the African Union Commission
chairman and the UN High Commissioner for Human Rights have called for
normalcy to be restored.

##  4 Result and Discussion

In this section, we present relevant results and discussions about the main
findings of the research.

###  4.1 Stakeholders in the online activism

Twitter offers unique features to understand when and where an event (tweet)
happened. The dataset we examined in this study contains information about the
user’s location, including the sources or devices used by the online
protesters. Although we can not ascertain the reliability of the user’s
reported data due to inaccuracies or false information provided by users, the
objective is to analyse how the location and device information can be
leveraged to understand the stakeholders involved in the online protest. Of
interest is to understand the role of national and international (the diaspora
community) in the protest.

##### Location

information about the users can inform whether the influential stakeholders in
the protest are residents or overseas. We acknowledge that the location
feature on Twitter may not be an accurate indicator of the location, but will
be useful in shading some insights and informing the analysis. As mentioned
earlier, Figure 2 illustrates the level of participation in the protest across
the 36 states, including the Federal Capital Territory (FCT Abuja), of the
federation. The protest is more prominent in Lagos 61.5%, FCT Abuja 7.11%, Oyo
3.6%, Delta 1.42%, Ondo 1.17%, and Rivers 1.17% states. Thus, the high
percentage of participation from Lagos state is in line with media report of
Lagos being the hub of the #EndSARS
protest777https://www.washingtonpost.com/outlook/2020/10/25/roots-endsars-
protests-nigeria/,888https://www.aljazeera.com/news/2020/10/22/timeline-on-
nigeria-unrest. As seen in Figure 3, the diaspora community was quite active
during the online protest.

Figure 2: Proportion of the #EndSARS online protest across the 36 states in
Nigeria, including the FCT, Abuja. Figure 3: Proportion of the #EndSARS online
protest across the globe. There is a high proportion of engagement with the
protest themes in the United States of America, United Kingdom and Canada. We
can see some moderate engagements from South Africa, Ghana, Uganda, Liberia,
Paraguay, Saudi Arabia, India, China, Indonesia, Malaysia, Cambodia, Turkey,
and most of Western Europe Countries.

##### Device

The type of device used by a user could reveal how mobile the user is. We
could infer how individuals roam from one point to another to join in online
protests. Suppose the device type is desktop computer, then the user will be
considered not mobile, and could point to an organisation with dedicated
personnel to keep the online protest alive. Because there are numerous devices
used by users in the data collection, we place the devices into 3 broad
clusters consisting of third-party sources 2%, mobile devices 88%, and Twitter
for web apps 10%, see Figure 10(b). The high proportion of mobile devices is
suggestive of high mobility among the protesters and enables them to
simultaneously participate in both offline and online protests.

###  4.2 Protest Themes and Public Perception

##### Protest Themes

It is vital to understand the kind of topics associated with the #EndSARS
protest on Twitter. To achieve that, we perform topic modelling on the content
of the raw tweets (see Table 2) using the Latent Dirichlet Allocation (LDA)
algorithm [37] and the Continuous Dirichlet Allocation (CLDA) algorithm [38]
for a better understanding of the topics in the data. Before proceeding with
the topic analysis, the tweets collection is subjected to a cleaning process
to get rid of unwanted content often associated with data from Twitter [39].
The preprocessing step involves tokenisation, stopwords removal and text
formatting. For normalisation, we remove urls, user mentions, emojis from the
collection. Figure 4 shows some of the relevant topics obtained from applying
the LDA algorithm. For readability and ease of interpretation, we decompose
the data into eight (8) different segments. For each segment, we limit our
analysis to the ten (10) top topics to understand the meaning and context of
the discussion topics. Figures 4 and 5 show the respective topics under each
segment.

Figure 4: An overview of the main topical issues related to the protest from
2017 to March 2021. From 2017 to early 2020 the discussion topics are centred
around the brutality of the SARS and advocating for support to the #EndSARS
campaign. Figure 5: An overview of the main topical issues related to protest
from April 2021 to December 2021. This period witnessed a high volume of
activity and discussion about the protest. During this period, there is an
inclusion of political movements intertwined with the protest theme.

##### Public Perception

Alongside the topical analysis, we are interested in knowing the nature or
sentiment expressed in the online discourse on #EndSARS. To accomplish that,
we identify the most prominent topics during the period and pull out the
associated tweets from our collection to analyse the sentiments or public
perception of the protest’s themes. To understand the intensity or polarity of
the public opinions about the protest, we leverage the off-the-shelf VARDER
[40] tool999a sentiment analysis tool for determining the sentiment associated
with social media texts to obtain the sentiment (as positive, neutral or
negative) of each tweet. Figure 6 shows the result of the sentiment analysis
consisting of positive and negative tweets about the movement. The negative
tweets are mainly expressing the brutal actions of the SARS police while the
positive tweets are mostly associated with rallying support for the #EndSARS
campaign. According to Figure 6, the intensity of the negative sentiment in
2017-2018 is the highest. Noting how people tend to respond quicker to
negative emotion [41, 42], this could be suggestive of using some emotional
narratives or negative sentiment to generate some momentum and attract public
attention towards the campaign.

Figure 6: The polarity of sentiment associated with the #EndSARS topics from
2017 to 2021. While the positive sentiment is mostly associated with tweets
garnering public support for the movement, the negative sentiment is mainly
about dissatisfaction with the activities of the SARS unit.

###  4.3 Engagement Analysis

There are many ways to examine how users engage with each other on Twitter.
What constitutes engagement and how to measure it on Twitter has been analysed
in previous studies [43, 44]. We can capture engagement levels depending on
how often a given account performs the actions of retweeting (RT), tweet
liking (favourite count), replying and user mention. In this study, we focus
on measuring engagement intensity concerning online activities such as the
frequency of tweet generation, retweets, and replies. For the engagement
analysis, we categorise an account holder as influential if the user has
tweeted or posted at least 10 tweets about the #EndSARS protest. This is to
limit the number of irrelevant or insufficient tweets. Figures 7 and 8 show
the highest engaging users based on relative retweet and reply actions.
Figures 11 show the tweet count of the most active users in the overall data
collection and the collection with the highest engagement with the protest’s
themes. The figures also point to the possibility of using social bots to
promote the online movement noting the explicit ’bot’ usage in the account
name. The accounts with the highest engagement with the protest themes are not
influential in the literal sense of being a celebrity or known influential
user. For instance, one of the most active accounts in terms of retweeting
action is the @endsarsbot_ that retweeted 429 tweets from 2021-07-31 to
2021-12-27. The main task of the account is limited to retweeting and calling
out to some Twitter users as a way of attracting attention and promoting the
protest. Another active account is the @psarmmiey with 105 retweets from
2021-07-31 to 2021-12-27. Interestingly, the activity period of both
@endsarsbot_ and @psarmiey are the same (from 2021-07-31 to 2021-12-27) and
their action is limited to retweeting as a strategy to mobilise for the
protest. Similarly, the @TheEndSarsBot retweeted 38 tweets from 2021-11-30 to
2021-12-27.

Figure 7: The level of engagement according to (a) accounts with the highest
relative retweeting action in the overall collection (b) relative retweets in
accounts with the highest engagement with the protest themes. Figure 8: The
level of engagement according to (a) accounts with the highest relative
replying action in the overall collection (b) relative replies in accounts
with the highest engagement with the protest themes.

###  4.4 From #EndSARS to Demand for Change

In addition to the themes and public perception of the protest, it is crucial
to determine whether the protest is purely driven by the need to end the SARS
unit or not. Through the topic modelling, we were able to identify relevant
tweets from the collected data based on the detected themes, see Figure 5.
This is required in order to make sense of the topics in detail. According to
Figures 4 and 5, it appears that from 2017-2018, the major topics were geared
towards generating some momentum for the #EndSARS movement. Some examples
during this period include:

  * -

’extortion continue’

    * (a)

”This kind of extortion has to end, we will continue to demand #ENDSARS.
Kindly retweet so people would be aware of the kind of atrocity committed by
@PoliceNG”

  * -

’sure alot’

    * (a)

” ….kindly RT this to advice/warn our guys to be careful tonight as I am sure
alot of SARs will be on the road tonight.”

  * -

’OAPs use’

    * (a)

”I will implore our OAPs to use their position to enlighten the public and not
deceive them on the SARS matter. There is nothing to be politically correct
about in a life and death matter. It is the same common man’s kids that is
endangered. #EndSARS.

The last topic (’OPAs use’), relates to the tweets calling for ’On-air
Personalities (OAPs)’ to support and enlighten the public about the activities
of the SARS unit. Other online topical issues during the protest period
include police force and police brutality calling for the reform of the
Nigeria Police Force, which is attributed to the  Lekki toll gate in Lagos
incidence that resulted in the loss of lives and casualties in an attempt by
the police to disperse protesters101010https://www.bbc.co.uk/news/world-
africa-59300011. Although the majority of the online discourse on the protest
is on ending the SARS unit, we observe the emergence of different themes
concerning the hashtags used and the associated content. These hashtags are
about social reforms and questioning the style of governance. An example of
such hashtags with a political undertone is the #endbadgovernanceinnigeria
alluding to regime change (see Figure 10(a)). This and similar hashtags have
surfaced alongside the protest theme on Twitter. Also, there exists hashtags
and related tweets accusing the government in power of supporting boko haram,
and demanding for the president to resign. Overall, the #EndSARS discussions
in 2021 seem to revolve around the demand for justice for the protesters,
ending bad governance and change of government.

##  5 Conclusion

The Special Anti-Robbery Squad (SARS) is a special police unit under the
Nigeria Police Force tasked with the responsibility of fighting violent
crimes. Over the years, the unit has been accused of various human rights
abuse across the nation leading to one of the major protests in the country.
Due to the demographics of the protesters, the protest was quite popular on
various online social networks. Using the popular #EndSARS hashtag on Twitter
to draw attention to human rights violations labelled against the SARS unit,
the protest received huge attention within and outside the country. In this
study, we critically examined the evolution of the protest on Twitter, the
nature of engagement with the protest themes, the factors influencing the
protest and public perceptions about the online movement. We have examined how
social media users interact with the #EndSARS movement and how online
communities respond to the protest. Based on examining public perception, we
found that the #EndSARS-related hashtags have been used to report ill-
treatment by the SARS unit and to rally support for the protest. Needless to
say, the themes in the online discourse are heavily on ending SARS and
vicarious experience, however, there are topics around reforming the police
and demand for regime change. Injecting a political undertone could lead to
setbacks in social activism as it will likely deviate from the main objective
of the movement or provoke counter protest. In line with previous findings
[36], the following mobilisation strategies of calling-out celebrities, and
sharing direct stories and vicarious experiences have been used to promote the
protest. Based on the explicit ’bot’ suffix, there is some evidence that
suggests the use of automated accounts to promote the course of the protest.
Through location and device analysis, we studied the degree of participation
in the protest and how the protesters engage with the #EndSARS themes. Over
70% of the protest is confined within a few states in Nigeria. The diaspora
communities also lent their voices to the issue. The most active users are not
those with high followership. The majority of the protesters utilised mobile
devices, accounting for 88% to mobilise and report on the protest. Our future
study will explore the possibility of mapping out how the online protest
translated into physical violence or confrontation. Also, we will examine how
information, including misinformation, propagates within the network of the
protesters.

## Appendix

(a) One of the earliest tweets about the #ENDSARS movement.

(b) A tweet with video of police shooting in 2017. This has provoked wider
protest121212https://twitter.com/Blazey_Oye/status/936923719825367040

(c) A sample tweet from Amnesty International, Nigeria about handling of the
protest by the authority.

(d) A directive from the Government of Nigeria banning SARS.

Figure 9: Relevant tweets about the #EndSARS movement

(a) Some relevant hashtags

(b) Devices used by the online protesters.

Figure 10: The (a) main #EndSARS hashtag alongside hashtags calling for change
in the style of governance by the protesters (b) main devices used by the
protesters. Figure 11: The level of engagement according to (a) accounts with
the highest number of tweets in the overall collection (b) accounts with the
highest engagement with the protest themes.

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July 15, 2022

# Electronic phase diagram in Te-annealed superconducting FeTe1-xSex revealed
by magnetic susceptibility

Takenori Fujii1 Yu Uezono2 Takumi Otsuka2 Shotaro Hagisawa2 and Takao
Watanabe2 1Cryogenic Research Center1Cryogenic Research Center The University
of Tokyo The University of Tokyo Bunkyo Bunkyo Tokyo 113-0032 Tokyo 113-0032
Japan
2Graduate School of Science and Technology Japan
2Graduate School of Science and Technology Hirosaki University Hirosaki
University Hirosaki 36-8561 Hirosaki 36-8561 Japan Japan
<EMAIL_ADDRESS>
###### Abstract

Knowledge of the doping ($x$)-temperature ($T$) phase diagram of Fe-based
superconductors is crucial in understanding the mechanism of high transition
temperature superconductivity. Here, we measured the Se doping dependence of
the magnetic susceptibility for Te-annealed FeTe1-xSex. Two characteristic
temperatures $T^{*}_{\chi}$ and $T^{**}_{\chi}$ were observed in the
temperature dependence of magnetic susceptibility, where the magnetic
susceptibility decreased below $T^{**}_{\chi}$ and tended to increase with
further decreasing temperature below $T^{*}_{\chi}$. The decrease in magnetic
susceptibility below $T^{**}_{\chi}$ is considered to be due to the opening of
the pseudogap. Whereas the increase in magnetic susceptibility below
$T^{*}_{\chi}$ is attributed to the increase in the carrier concentration of
electrons. Furthermore, we found the large superconducting fluctuation, which
may be related to BCS-BEC crossover.

FeTe1-xSex single crystals, Te-annealing, normal state magnetic
susceptibility, pseudogap, crossover from the incoherent to the coherent
electronic state, BCS-BEC crossover

##  1 Introduction

Normal state properties of iron-based superconductors have been crucial in
understanding the mechanism of superconductivity, and they have been garnering
increasing attention, since the discovery of their high superconducting
transition temperature $T_{c}$ [1]. Various problems with this material, such
as the anomalous non-Fermi-liquid-like normal-state transport properties[2]
and the possibility of the Bardeen-Cooper-Shrieffer (BCS) - Bose-Einstein
condensation (BEC) crossover regime[3, 4, 5, 6, 7], are particularly in the
forefront of condensed matter physics. Among the several Fe-based
superconductors, the FeTe1-xSex system has an advantage in addressing the
aforementioned problems because its crystal structure is the simplest, i.e, it
comprises only conducting FeX (X: Te or Se) layers. However, excess Fe is
inevitably incorporated in the crystals, which conceals the nature of
anomalous physical properties in FeTe1-xSex systems. Hence, a lot of efforts
have been made to eliminate obstructive excess Fe[8, 9, 10, 11]. In our
previous research, we developed an annealing method that discards excess Fe by
annealing single crystals in tellurium vapor (Te anneal)[12]. Using this Te-
annealing method, the excess Fe was sufficiently eliminated without damaging
the samples. With this high quality sample, we performed the magneto-transport
measurements and inferred that the crossover from the incoherent to the
coherent electronic state and the opening of the pseudogap occur at high
temperatures[13]. Furthermore, via magnetoresistance measurements, we
determined that the temperature $T_{scf}$ at which the superconducting
fluctuations occur was 2.7 times larger than $T_{c}$, which is consistent with
the behavior of the BCS-BEC crossover regime[14].

The evolution from incoherent to coherent electronic states with increasing Se
doping was also observed by angle-resolved photoemission spectroscopy (ARPES),
which elucidates the close relationship between the coherent electronic state
and emergence of superconductivity[15, 16]. On the other hand, whether iron-
based superconductors, especially FeSe and FeSe1-xSx are in the BCS-BEC
crossover regime or not is hotly debated relative to the giant superconducting
fluctuations[3, 4, 5, 6, 7]. Therefore, clarifying the doping
($x$)-temperature ($T$) phase diagram of Fe-based superconductors by using
various measurements is important in elucidating the mechanism of
superconductivity. Here, we measured the normal state magnetic susceptibility
of Te annealed FeTe1-xSex ($x$ = 0.2, 0.3, and 0.4) and investigated the
doping ($x$)-temperature ($T$) phase diagram.

##  2 Experiment

Single crystals of FeTe1-xSex were grown using the Bridgman method[17] with
their nominal compositions. As-grown crystals were cleaved into thin crystals
with 1-mm thickness, and they were sealed into pyrex or quartz tube with
pulverized Te. Then, the tube was heated for more than 400 h at 400 ∘C.
Annealed crystals were usually covered with grayish accretion. However, by
carefully removing the accretion, shiny and flat surface emerged. The
superconducting transition of the annealed crystals were very sharp ($\Delta
T_{c}\leq$ 1K), thus indicating that the excess iron was completely discarded.
Magnetic susceptibility was measured using a superconducting quantum
interference device (SQUID) magnetometer (Quantum Design MPMS3) with the
magnetic field applied parallel to the thin sample.

##  3 Results and Discussion

###  3.1 Impurity phase of Fe3O4 in the Te-annealed samples

Figure 1(a) presents the temperature dependence of the magnetic susceptibility
for as-grown FeTe0.6Se0.4. It exhibits Curie-Weiss-like behavior at low
temperatures and slight symptoms of superconductivity below 5K. This Curie-
Weiss-like behavior is attributed to the local moment from excess Fe; in
addition, superconductivity is destroyed by the local moment. Below 50 K, the
difference in susceptibility at each magnetic field is evident. The inset of
Figure 1(a) illustrates the magnetic field dependence of the magnetic moment
($M-H$ plot). It presents the linear field dependence at high temperatures,
while the deviation from the linear field dependence was observed at 10 K.
These results indicate that the excess Fe works as local moment at high
temperatures and that the ferromagnetic interaction of excess Fe would develop
below 50 K. Figure 1(b) presents the temperature dependence of the
magnetization for Te-annealed FeTe0.6Se0.4 measured at 7 T. It exhibits an
almost temperature independent behavior, which implies that Pauli
paramagnetism is dominant. The inset of Figure 1(b) presents a $M-H$ plot for
Te-annealed FeTe0.6Se0.4. We can clearly observe the ferromagnetism, which
could have emerged from the impurity phase other than excess Fe. To extract
the Ferromagnetic component from the obtained susceptibility of Te-annealed
sample, we deduced residual magnetic moment at 0 Oe, which is the
$y$-intercept of linear magnetic moment in $M-H$ plot. Using the temperature
dependence of the magnetic moment at 7 T ($M_{7T}(T)$) and 1 T ($M_{1T}(T)$),
the residual magnetization $M_{res}(T)$ was calculated using the equation,

$M_{res}(T)=M_{1T}(T)-\frac{M_{7T}(T)-M_{1T}(T)}{6}\times 1.$ (1)

Figure 1(c) presents the calculated residual magnetic moment, which emerges
from the impurity phase. As observed in the figure, clear phase transition can
be detected at approximately 120 K. This is considered a Verwey transition in
magnetite (Fe3O4)[18]. Note that, there are no symptoms of transition around
120 K in the original FeTe0.6Se0.4 data, which suggests that the inclusion of
the impurity phase (Fe3O4) was negligible. Because the saturated magnetization
of magnetite is known to be approximately 90 emu/g at room temperature, we can
estimate the impurity phase amount of magnetite as 2.46 $\times$ 10-3 mg in
5.34 mg FeTe0.6Se0.4 (0.046 %). The amount of the impurity phase does not
depend on Se doping, but on the position of the samples. Because this impurity
phase is absent in the as-grown samples, it is considered to have been
introduced during the annealing process. In the following analysis, this
ferromagnetic component was subtracted from the raw data. However, our
conclusion was not altered depending on the details of subtraction.

###  3.2 Estimation of characteristic temperatures

Figure 2(a) illustrates the temperature dependence of magnetic susceptibility
of the samples with various Se doping. It exhibits a rather large
susceptibility (4 - 9 $\times$ 10-6 emu/gOe), which is 10 times larger than
that of high-$Tc$ cuprate Bi2Sr2CaCu2O8-δ[19]. The observed large
susceptibility is consistent with a previous report[20]. The absolute values
of the magnetic susceptibility increase drastically with decreasing Se
contents. Because Pauli paramagnetism would be dominant in the magnetic
susceptibility in FeTe1-xSex, the increase in the magnetic susceptibility
implies the increase in DOS at the Fermi level. In fact, such an increase in
DOS was observed in the specific heat measurement, where, the electronic
specific-heat coefficient in the normal state $\gamma_{n}$ increases as Se
decreases[21]. Because the carrier density would not change drastically (Te is
an isovalent substitution), the increase in the effective mass due to strongly
correlated electron would be realized toward a quantum critical point between
the antiferromagnetic and superconducting phases ($\sim$ $x$ = 0.07).

The overall temperature dependence of the magnetic susceptibility in
FeTe1-xSex is as follows. With decreasing temperature, the magnetic
susceptibility decreases below $T^{**}_{\chi}$ (indicated by red arrows). With
further decreasing temperature, slight upturn can be observed below
$T^{*}_{\chi}$ (indicated by blue arrows). To estimate the characteristic
temperatures $T^{*}_{\chi}$, $T^{**}_{\chi}$, and $T_{scf}$ in the magnetic
susceptibility, we plotted the temperature derivative of magnetic
susceptibility vs temperature for $x$ = 0.2, 0.3, and 0.4 in Figure 2(b),
2(c), and 2(d) respectively. As observed in these figures, the temperature
derivative changes its slope twice with decreasing temperature. Hence, we
present the solid straight lines that are linear extrapolations at each
temperature ranges. $T^{*}_{\chi}$ and $T^{**}_{\chi}$ were defined from the
intersection point of the extrapolation lines. Similarly, $T_{scf}$ was
determined by the temperature from which the temperature derivative start to
deviate from the linear extrapolation line. The obtained temperatures are
consistent with the observations of our magnetotransport measurements[13].

Figure 3 presents the $x-T$ phase diagram for FeTe1-xSex, including the data
from a previous study[13]. $T^{**}_{\chi}$ corresponds to $T^{*}_{\rho ab}$ at
which $\rho_{ab}$ reaches its broad maximum. The decrease in magnetic
susceptibility below $T^{**}_{\chi}$ is considered to be due to the decrease
in DOS by opening the pseudogap. In strongly correlated iron chalcogenides,
such as FeTe1-xSex, the existence of an orbital-selective Mott phase (OSMP)
and related incoherent to coherent transition were theoretically proposed[22,
23]. As explained in a previous report[13], $T^{**}_{\chi}$ would correspond
to the transformation from OSMP to the metallic state. Recently, a similar
phase diagram was proposed using the ARPES measurement[24]. When the states
become coherent, the Fermi surfaces become well defined with some type of band
hybridization, which would cause the pseudogap to open via interband
nesting[13]. On the other hand, another characteristic temperature
$T^{*}_{\chi}$ appears to correspond with $T^{*}_{\rho c}$, below which
$\rho_{c}$ values exhibit the typical plateau. As mentioned in a previous
report, the electron carriers would participate in charge transport below this
temperature; hence, magnetic susceptibility would increase due to the increase
in DOS[13]. As observed in Fig. 2(a), the magnetic susceptibility decreased
again below $T_{scf}$ when the temperature was further decreased (indicated by
green arrows). We consider that the decrease in magnetic susceptibility is
attributed to the diamagnetism originated in superconducting fluctuation. The
estimated $T_{scf}$ values from Fig. 2(b)-(d) were $\sim$ 57 K for $x$ = 0.4,
$\sim$ 45 K for $x$ = 0.3, and $\sim$ 31 K for $x$ = 0.2. Notably, they were
3.9, 3.2, and 2.4 times larger than their corresponding $T_{c}$ for $x$ = 0.4,
$x$ = 0.3, and $x$ = 0.2 respectively. In the BCS-BEC crossover regime, the
effect of superconducting fluctuations is expected to be enhanced, as Cooper
pairs can be formed at higher temperatures than $T_{c}$[3]. These results
indicate that the FeTe1-xSex system is indeed in the BCS-BEC crossover regime.

##  4 Conclusion

To estimate characteristic temperatures, such as $T^{**}_{\chi}$,
$T^{*}_{\chi}$, and $T_{scf}$, we measured the magnetic susceptibility for
high-quality Te-annealed FeTe1-xSex. The absolute value of magnetic
susceptibility increased as Se contents decreased, which is considered to be
due to the increase in DOS as it approaches a quantum critical point between
the antiferromagnetic and superconducting phases. We observed the decrease in
magnetic susceptibility below $T^{**}_{\chi}$, which is considered to be due
to the opening of the pseudogap. On the other hand, the increase in magnetic
susceptibility below $T^{*}_{\chi}$ is attributed to the increase in DOS due
to the participant of electron carrier. These results agree with our previous
magnetotransport study[13]. Moreover, we inferred that $T_{scf}$ values were
substantially high and they reached 57, 45, and 31 K for $x$ = 0.4, 0.3, and
0.2 respectively. In particular, it was 3.9 times larger than its $T_{c}$ for
$x$ = 0.4. These high $T_{scf}$ values are consistent with the behavior of the
BCS-BEC crossover regime.

In this study, we determined that our Te-annealed sample contained a
ferromagnetic impurity phase. Although the amount of this impurity phase is
negligible, it may conceal the intrinsic behaviors of superconductivity at a
low field. In the future, we have to improve the annealing process, to
completely eliminate ferromagnetic impurity and reveal more detailed magnetic
properties.

## Acknowledgment

This work was supported by JSPS KAKENHI Grant No. 20K03849 and the Hirosaki
University Grant for Distinguished Researchers from the fiscal year 2017 to
2018.

## Figure captions

Figure 1: (a): Temperature dependence of the magnetic susceptibility for as-
grown sample of $x$ = 0.4. (b): Temperature dependence of the magnetization
for Te-annealed sample of $x$ = 0.4 measured at 7 T. The blue line presents
the data that the ferromagnetic component from Fe3O4 was subtracted. Inset of
Fig 1(a) and (b): Magnetic field dependence of the magnetization. (c):
Temperature dependence of calculated residual magnetic moment that indicates
the magnetic moment of the impurity phase magnetite (Fe3O4). Figure 2: (a):
Temperature dependence of the magnetic susceptibility of the Te-annealed
sample with various Se doping measured at 7 T. (b), (c), (d): Temperature
derivative of the magnetic susceptibility vs temperature for $x$ = 0.2, 0.3,
and 0.4 respectively. The solid straight lines represent linear extrapolations
at a certain temperature range, which are presented as a guideline. Figure 3:
Characteristic temperatures $T^{*}_{\chi}$, $T^{**}_{\chi}$, and $T_{scf}$ vs
Se concentration $x$ for Te-annealed FeTe1-xSex, plotted together with data
from previous magneto transport study[13]. The open circles of $T^{*}_{RH}$
are replotted from Ref. [25].

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