Conductance properties of an $\alpha$-$T_3$ Corbino disk

TL;DR

This paper analyzes the conductance and transport properties of an $oldsymbol{ extalpha}$-$ extbf{T}_3$ lattice in a Corbino disk geometry, revealing quantum interference effects, AB oscillations, and the influence of flat bands on electron transport.

Contribution

It provides an exact analytical study of conductance in an $oldsymbol{ extalpha}$-$ extbf{T}_3$ Corbino disk, highlighting the role of flat bands and parameter effects on quantum transport features.

Findings

Periodic Aharonov-Bohm oscillations in conductance

Emergence of higher harmonic modes and split-peak structures

Transition of Fano factor indicating different transport regimes

Abstract

In this work, we investigate an $\alpha$-$T_3$ lattice in the form of a Corbino disk, characterized by inner and outer radii $R_1$ and $R_2$, threaded by a tunable magnetic flux. Through exact (analytic) solution of the stationary Dirac-Weyl equation, we compute the transmission probability of the carriers and hence obtain the conductance features for $0<\alpha \leq 1$ ($\alpha$ denotes the strength of the hopping between the central atom and one of the other two) which allows ascertaining the role of the flat band, alongwith scrutinizing the transport features from graphene to a dice lattice. Our results reveal periodic Aharonov-Bohm (AB) oscillations in the conductance, reminiscent of the utility of the Corbino disk as an electron pump. Further, these results are strongly influenced by parameters, such as, doping level, ratio of the inner and outer radii, magnetic flux, and $\alpha$. Additionally, complex quantum interference effect resulting in the possible emergence of higher harmonic modes and split-peak structures in the conductance, become prominent for smaller $\alpha$ values and larger ratios of the radii. We also find that, away from the charge-neutrality point (zero doping), the conductance oscillations are more pronounced and sensitive to the various parameters, with the corresponding behaviour largely governed via the evanescent wave transport. The Fano factor reveals distinct transport regimes, transitioning from Poissonian to pseudo-diffusive for $\alpha < 1$, and from ballistic to pseudo-diffusive for $\alpha = 1$. This setup, thus serves as a fertile ground for studying the generation of quantum Hall current and Aharonov-Bohm (AB) oscillations in a flat band system, alongwith demonstrating intricate appearance of higher harmonics in electron transport.