Detect axial gauge fields with a calorimeter

Matteo Baggioli,Maria Vozmediano,Karl Landsteiner,Maxim N Chernodub

doi:10.21468/scipostphyscore.3.2.013

Abstract

Torsional strain in Weyl semimetals excites a unidirectional chiral density wave propagating in the direction of the torsional vector. This gapless excitation, named the chiral sound wave, is generated by a particular realization of the axial anomaly via the triple-axial (AAA) anomalous diagram. We show that the presence of the torsion-generated chiral sound leads to a linear behavior of the specific heat of a Weyl semimetal and to an enhancement of the thermal conductivty at experimentally accessible temperatures. We also demonstrate that such an elastic twist lowers the temperature of the sample, thus generating a new, anomalous type of elasto-calorific effect. Measurements of these thermodynamical effects will provide experimental verification of the exotic triple-axial anomaly as well as the reality of the elastic pseudomagnetic fields in Weyl semimetals.

Highlights

Weyl semimetals (WSM) represent today a perfect bridge between high and low energy physics
The density of states at the Fermi level in TaAs has been measured to be D(εF ) ∼ 1018−1019 cm−3 [33] what gives a ratio for the linear contribution to the heat capacity coming from the Sommerfeld contribution and the linear term generated by the chiral sound wave of γel(T, μ) ∼ 10−2. γCSW(T )
- we have neglected all the effects coming from the coupling between the chiral sound wave and the acoustic phonons since they are negligible in the low temperature limit

Summary

Introduction

Weyl semimetals (WSM) represent today a perfect bridge between high and low energy physics. The fact that their electronic excitations reveal themselves as massless Dirac fermions in three space dimensions provides an alternative lab to the quark-gluon plasma to study the phenomenology of chiral fermions. Quantum anomalies [1] and anomaly-induced transport responses [2, 3] are the most prominent phenomena generating research works from the high and low energy physics communities. Coming from a bosonic mode, it contributes to the violation of the Wiedemann-Franz relation This observation will provide evidences for the contribution to the AAA triangular diagram to the anomaly [2], and for the reality of elastic axial pseudomagnetic fields

The chiral sound wave

Specific heat

Experimental accessibility

Thermal conductivity

Elasto-caloric effect

Summary and discussion