Interaction-induced conductance from zero modes in a clean magnetic graphene waveguide

TL;DR

This paper investigates how Coulomb interactions induce conductance in zero-energy flat bands of a magnetic graphene waveguide, revealing a non-quantized, interaction-dependent conductance that serves as a probe of electron-electron interactions.

Contribution

It demonstrates that Coulomb interactions enable conductance in zero-energy flat bands of a graphene waveguide, a phenomenon not described by traditional models like Tomonaga-Luttinger liquids.

Findings

Coulomb interactions induce conductance in zero-energy flat bands.

Conductance depends on zero-mode filling and is not quantized.

Proposes a new method to probe electron-electron interactions in graphene.

Abstract

We consider a waveguide formed in a clean graphene monolayer by a spatially inhomogeneous magnetic field. The single-particle dispersion relation for this waveguide exhibits a zero-energy Landau-like flat band, while finite-energy bands have dispersion and correspond, in particular, to snake orbits. For zero-mode states, all matrix elements of the current operator vanish, and a finite conductance can only be caused by virtual transitions to finite-energy bands. We show that Coulomb interactions generate such processes. In stark contrast to finite-energy bands, the conductance is not quantized and shows a characteristic dependence on the zero-mode filling. Transport experiments thereby offer a novel and highly sensitive probe of electron-electron interactions in clean graphene samples. We argue that this interaction-driven zero-mode conductor may also appear in other physical settings and is not captured by the conventional Tomonaga-Luttinger liquid description.