Anomalous Defects and Their Quantized Transverse Conductivities

TL;DR

This paper models defects in solids using 3D gravity, revealing chiral bound states localized on disclinations and screw dislocations, which lead to anomalous transverse conductivities due to their effective 1+1D chiral fermion behavior.

Contribution

It introduces a gravity-based description of solid defects and uncovers chiral bound states that influence electronic transport properties in novel ways.

Findings

Chiral bound states are localized on defects.

Effective field theory of chiral fermions describes these states.

Anomalous electromagnetic responses lead to unique conduction properties.

Abstract

Using a description of defects in solids in terms of three-dimensional gravity, we study the propagation of electrons in the background of disclinations and screw dislocations. We study the situations where there are bound states that are effectively localized on the defect and hence can be described in terms of an effective 1+1 dimensional field theory for the low energy excitations. In the case of screw dislocations, we find that these excitations are chiral and can be described by an effective field theory of chiral fermions. Fermions of both chirality occur even for a given direction of the magnetic field. The ``net'' chirality of the system however is not always the same for a given direction of the magnetic field, but changes from one sign of the chirality through zero to the other sign as the Fermi momentum or the magnitude of the magnetic flux is varied. On coupling to an external electromagnetic field, the latter becomes anomalous, and predicts novel conduction properties for these materials.