Pressure-Driven Magneto-Topological Phase Transition in a magnetic Weyl semimetal

TL;DR

This study demonstrates a pressure-induced magneto-topological phase transition in a magnetic Weyl semimetal, revealing how external pressure can modulate topological states and magnetic phases in such materials.

Contribution

It provides the first experimental observation and theoretical analysis of pressure-driven changes in magnetic and topological phases in a magnetic Weyl semimetal.

Findings

Identification of a pristine Weyl phase with additional Weyl nodes at low pressure

Observation of a transition to a Z2 topological insulator phase after symmetry restoration

Discovery of a unique band crossing leading to Weyl node annihilation across spin channels

Abstract

The co-occurrence of phase transitions with local and global order parameters, such as the entangled magnetization and topological invariant, is attractive but has been seldom realized experimentally. Here, by using high-pressure in-situ X-ray diffraction, high-pressure electric transport measurements and high-pressure first-principles calculations, we report a magneto-topological phase transition, i.e., the phenomenon of magnetic materials undergoing different magnetic and topological phases during the process of pressure loading, in a recently discovered magnetic Weyl semimetal Co3Sn2S2. By considering both out-of-plane ferromagnetic and in-plane anti-ferromagnetic components, the calculated results can well fit the experimental data. The calculation results furtherly reveal a pristine Weyl phase with four more pairs of Weyl nodes under low pressures, and a generally-defined Z2 topological insulator phase after the restoration of time-reversal symmetry. Remarkably, the present magneto-topological phase transition involves a pair of crossing bands of two spin channels becoming degenerate. Thus, all the chiral Weyl nodes annihilate with their counterparts from another spin channel, in contrast to the typical annihilation of Weyl pairs from the same bands in inversion-asymmetric systems. Our experiments and theoretical calculations uncover a manner to modulate the diverse topological states by controlling the internal exchange splitting via external physical knobs in topological magnets.