Entropy in engineered quantum systems - mesoscopic thermodynamics of correlated quantum states
Quantum systems that have been engineered to host correlated electronic states are of outstanding fundamental and technological interest. Often ‘exotic’ new quasi-particles emerge, such as Majorana fermions, whose inherent topological robustness forms the basis of a promising approach to quantum computation. Another recent example are sheets of pencil-lead graphene which superconduct with a proper twist between layers.

Thermodynamic probes have been central for characterising new phases of matter in bulk materials. Low-dimensional systems offer greater opportunities for control, but probing their electronic states in a similar way is notoriously difficult, in part because of the small number of electrons involved.

The objective of this project is to overcome this challenge and to develop a unique conceptual and experimental foundation for exploring correlated quantum states in low-dimensional systems by measuring thermodynamic quantities, in particular entropy. Entropy is one of the most fundamental of physical properties, and in recent years has been recognized as a key to understanding systems as diverse as qubits and black holes. Fully exploiting entropy measurements in mesoscopic physics will open up a new window to a mechanistic understanding of correlated quantum states in engineered structures, with promise for ground-breaking novel device paradigms.

Members of the consortium have pioneered some of the few existing approaches to making thermodynamic measurements of low-dimensional systems. In combining our expertise, we will develop, test and explore a versatile suite of thermodynamic probes, and in particular i) demonstrate fractional entropy as an unequivocal observable for exotic states, including Majorana fermions; ii) develop thermodynamic measurement paradigms to probe correlated states in novel materials, in particular twisted bilayer graphene; and iii) achieve the first-time measurement of macroscopic entanglement entropy in solid-state systems.