Berry curvature generation detected by Nernst responses in ferroelectric Weyl semimetal.

Zhang, Cheng-Long; Liang, Tian; Bahramy, M S; Ogawa, Naoki; Kocsis, Vilmos; Ueda, Kentaro; Kaneko, Yoshio; Kriener, Markus et al. · Proc Natl Acad Sci U S A · 2021

basic_science · Level V

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Abstract

The quest for nonmagnetic Weyl semimetals with high tunability of phase has remained a demanding challenge. As the symmetry-breaking control parameter, the ferroelectric order can be steered to turn on/off the Weyl semimetals phase, adjust the band structures around the Fermi level, and enlarge/shrink the momentum separation of Weyl nodes which generate the Berry curvature as the emergent magnetic field. Here, we report the realization of a ferroelectric nonmagnetic Weyl semimetal based on indium-doped Pb<sub>1-</sub> <i><sub>x</sub></i> Sn <i><sub>x</sub></i> Te alloy in which the underlying inversion symmetry as well as mirror symmetry are broken with the strength of ferroelectricity adjustable via tuning the indium doping level and Sn/Pb ratio. The transverse thermoelectric effect (i.e., Nernst effect), both for out-of-plane and in-plane magnetic field geometry, is exploited as a Berry curvature-sensitive experimental probe to manifest the generation of Berry curvature via the redistribution of Weyl nodes under magnetic fields. The results demonstrate a clean, nonmagnetic Weyl semimetal coupled with highly tunable ferroelectric order, providing an ideal platform for manipulating the Weyl fermions in nonmagnetic systems.