Conductance anomaly near the Lifshitz transition in strained bilayer graphene

TL;DR

This paper investigates how strain-induced Lifshitz transitions in bilayer graphene cause conductance anomalies in ballistic junctions, revealing orientation-dependent non-monotonic behavior near the transition.

Contribution

It demonstrates the conductance anomaly near the Lifshitz transition in strained bilayer graphene and how it depends on crystallographic orientation and junction type.

Findings

Conductance shows non-monotonic temperature dependence near the Lifshitz transition.

Anomaly appears only in junctions between regions of different polarity.

Effect depends on the crystallographic orientation of strain.

Abstract

Strain qualitatively changes the low-energy band structure of bilayer graphene, leading to the appearance of a pair of low-energy Dirac cones near each corner of the Brillouin zone, and a Lifshitz transition, (a saddle point in the dispersion relation) at an energy proportional to the strain [M. Mucha-Kruczynski, I.L. Aleiner, and V.I. Fal'ko, Phys. Rev. B 84, 041404 (2011)]. Here, we show that in the vicinity of the Lifshitz transition the conductance of a ballistic n-p and n-p-n junction exhibits an anomaly: a non-monotonic temperature and chemical potential dependence, with the size depending on the crystallographic orientation of the principal axis of the strain tensor. This effect is characteristic for junctions between regions of different polarity (n-p and n-p-n junctions), while there is no anomaly in junctions between regions of the same polarity (n-n' and n-n'-n junctions).