reciprocity enforces $(\alpha_{m1}^{e2})_{z}^{xy}$ = $(\alpha_{e2}^{m1})_{xy}^{z}$. Interestingly, $(\alpha_{m1}^{m1})_{z}^{z}$, $(\alpha_{e2}^{e2})_{xy}^{xy}$, and $(\alpha_{e2}^{m1})_{xy}^{z}$ have very similar spectral feature resembling Lorentzian resonances, indicating that some components may additionally be coupled together possibly using singular value decomposition technique [@Suryadharma2019] or modular analysis [@Asadchy2019].

![(a) The schematics of twisted double-bars. (b) Retrieved $\boldsymbol{\alpha}$-tensor at $\lambda=520~\text{nm}$. (c) Extinction and (d) circular dichroism at planewave incidence propagating in $x$-, $y$-, and $z$-directions. (e) Spectra of $(\alpha_{e1}^{e1})_{x}^{x}$, $(\alpha_{e1}^{e1})_{z}^{z}$, $(\alpha_{e2}^{e1})_{xy}^{z}$, $(\alpha_{e1}^{m1})_{z}^{z}$, and $(\alpha_{m1}^{m1})_{z}^{z}$. Geometrical parameters are: radius 20 nm, length 100 nm, gap distance 20 nm, and twist angle 45$^\circ$.[]{data-label="fig:TDB"}](Fig_TDB.png)

Plasmonic chiral particles have exhibited chiral responses far-exceeding those from natural materials. Among them, a twisted double-bars (TDB) has been widely used to generate exceptionally strong chiral responses [@Auguie2011], which we assess from circular dichroism (CD). Different from PDB, TDB is geometrically chiral, and therefore parity-odd, and $\alpha_{e1}^{m1}$, $\alpha_{m1}^{e1}$, $\alpha_{e2}^{e1}$, and $\alpha_{e1}^{e2}$ transition components are now allowed. An important property of TDB is strongly anisotropic CD, which is only visible for the light propagation parallel to the twist-axis ($\hat{y}$). Interestingly, this anisotropic CD cannot be explained by dipolar $\boldsymbol{\alpha}$-tensor alone, because $(\alpha_{e1}^{m1})_{z}^{z}$ and $(\alpha_{m1}^{e1})_{z}^{z}$ contribute to chiral response for both $\mathbf{k \parallel x}$ and $\mathbf{k \parallel y}$. We confirmed that 