Anomalous Nernst Effect in Nonmagnetic Nodal Line Semimetal PbTaSe$_2$

TL;DR

This paper reports the observation of an anomalous Nernst effect in the nonmagnetic topological semimetal PbTaSe$_2$, linked to its nodal line Berry curvature, and how it changes across a structural phase transition.

Contribution

It demonstrates the presence of an anomalous Nernst effect in a nonmagnetic nodal line semimetal and links it to the evolution of nodal lines during a structural transition.

Findings

Anomalous Nernst effect observed in PbTaSe$_2$

Amplitude of the effect decreases across the structural transition

Nodal line structures are partially annihilated during the transition

Abstract

PbTaSe$_2$ is a unique topological material, in which the number of nodal lines is expected to change at the structural transition between the lower temperature/pressure "L" phase and the higher temperature/pressure "H" phase. We report the anomalous Nernst effect attributed to the Berry curvature of nodal lines and its change with the structural transition. In the L phase, the Nernst coefficient ($S_{yx}$) shows the step-like magnetic field dependence reminiscent of the anomalous Nernst effect of nonmagnetic Dirac/Weyl semimetals. By applying hydrostatic pressure, we discovered that the amplitude of the anomalous component significantly decreases at the transition to the H phase, which might correspond to the partial annihilation of nodal line structures.