by
DrCheng-Long Zhang(RIKEN Center for Emergent Matter Science (CEMS))
→
Asia/Shanghai
TDLI Meeting Room 200
TDLI Meeting Room 200
Description
Abstract
Weyl semimetal is a class of crystalline materials with nondegenerate linear band dispersions, which can be described by Weyl equation. The low energy excitations are called Weyl fermions, which have well-defined chirality near the crossing point. As behaving like magnetic monopoles live in even space-time dimension, Weyl fermions inherit its accidental crossing property solely dependent on the codimension, namely requiring no additional symmetry protection excepting the translational symmetry. This ‘accidental’ property makes the first theoretical prediction of nonmagnetic Weyl semimetal of TaAs family more difficult and slower than we expected. I will talk about transport, magnetic torque measurements of single crystalline TaAs and show Chiral anomaly, Weyl annihilation and non-saturating magnetization related experimental behaviors [1-3]. However, the difficulty for discovering a tunable and ideal Weyl semimetal still exists, even though many theoretical advances have been made recent years. In the second part, I will present our recent progress on how to access a tunable and pure Weyl state just by experimental engineering (without DFT), namely through a famous paradigm proposed by Murakami almost 15 years ago. I will show a highly tunable materials system for topological semimetal, indium (In)-doped PbTe-SnTe alloy [4-5]. By exploring the crystals with varying Pb/Sn ratios and In doping levels, a phase with low carrier concentration, high mobility, and large in-plane (also out-plane) anomalous Hall/Nernst effect accompanied by sizable second harmonic generations is found for a finite area of the composition between topological crystalline insulator and normal insulator, at ambient pressure.
[1] C.-L. Zhang et al., Nature Communications 7: 10735 (2016).
[2] C.-L. Zhang et al., Nature Physics 13, 979-986 (2017).
[3] C.-L. Zhang et al., Nature Communications 10: 1028 (2019).
[4] C.-L. Zhang & T. Liang et al., Phys. Rev. Materials 4, 091201(R) (2020).
[5] C.-L. Zhang & T. Liang et al., In preparation.
