Pseudo Landau levels, negative strain resistivity, and enhanced thermopower in twisted graphene nanoribbons

TL;DR

This paper predicts that twisted graphene nanoribbons can host strain-induced pseudo Landau levels, leading to negative resistivity and enhanced thermopower, revealing new electronic responses without magnetic fields.

Contribution

It introduces the concept of pseudo Landau levels in twisted graphene nanoribbons and analyzes their effects on resistivity and thermopower.

Findings

Pseudo Landau levels are analytically solvable in twisted graphene nanoribbons.

Strain induces negative resistivity related to the chiral anomaly.

Thermopower is significantly enhanced when pseudo Landau levels are fully filled.

Abstract

As a canonical response to the applied magnetic field, the electronic states of a metal are fundamentally reorganized into Landau levels. In Dirac metals, Landau levels can be expected without magnetic fields, provided that an inhomogeneous strain is applied to spatially modulate electron hoppings in a similar way as the Aharonov-Bohm phase. We here predict that a twisted zigzag nanoribbon of graphene exhibits strain-induced pseudo Landau levels of unexplored but analytically solvable dispersions at low energies. The presence of such dispersive pseudo Landau levels results in a negative strain resistivity characterizing the $(1+1)$-dimensional chiral anomaly if partially filled and can greatly enhance the thermopower when fully filled.