Thermal and gravitational chiral anomaly induced magneto-transport in Weyl semimetals

Abstract

Quantum anomalies in Weyl semimetal (for either E · B = 0 or ∇T · B = 0) leads to chiral charge and energy pumping between the opposite chirality nodes. This results in chiral charge and energy imbalance between the Weyl nodes which manifests in several intriguing magneto-transport phenomena. Here, we investigate the role of electrical-, thermal-, and gravitational chiral anomaly on magneto-transport in Weyl semimetals. We predict the planar Ettinghausen and Righi-Leduc effect to be a distinct signature of these quantum anomalies. We also demonstrate a significant enhancement in the thermo-electric conductivity, Seebeck effect, Nernst effect and thermal conductivity with increasing temperature. Interestingly, this anomaly induced transport violates the Wiedemann-Franz law and Mott relation.

Chiral anomalies induced transport in Weyl metals in quantizing magnetic field

“…This manifests in the magnetothermal experiments in the form of positive magnetothermopower and positive magnetothermal conductivity [26][27][28][29], both of which have also been observed in recent experiments [30,31]. In addition to their manifestations in longitudinal magnetotransport, CAs have also been shown to give rise to the planar Hall effects in all transport coefficients [29,[32][33][34][35][36][37][38][39][40]. Recently, we predicted another anomaly, the thermal chiral anomaly in which a temperature gradient collinear with the magnetic field gives rise to charge and energy imbalance between the opposite chirality Weyl fermions [29].…”

“…In addition to their manifestations in longitudinal magnetotransport, CAs have also been shown to give rise to the planar Hall effects in all transport coefficients [29,[32][33][34][35][36][37][38][39][40]. Recently, we predicted another anomaly, the thermal chiral anomaly in which a temperature gradient collinear with the magnetic field gives rise to charge and energy imbalance between the opposite chirality Weyl fermions [29].…”

“…The carriers of the lowest LLs have a constant velocity, and are either left movers (for s = 1) or right movers (for s = −1). Next, we discuss the origin of quantum anomalies from the lowest chiral LLs and explore their manifestation in electric and thermal magnetotransport experiments in WM [25,27,29,41,52].…”

“…To evaluate this contribution, we will consider the chemical potential to be positive (μ > 0). Evaluating these expressions using integration by parts [28,29], we obtain j s e,eq = −e μC s 0…”

“…Thus, the existence of the chiral LLs is an essential ingredient to obtain the nonzero charge and energy currents for each node even in equilibrium. These chiral currents are in turn related to the CAs in WMs [27,29,52]. We had earlier derived equations similar to Eqs.…”