Field induced topological phase transition from a three-dimensional Weyl semimetal to a two-dimensional massive Dirac metal in ZrTe5

TL;DR

This study demonstrates a magnetic field-induced topological phase transition in ZrTe5, transforming a 3D Weyl semimetal into a 2D massive Dirac metal by annihilating Weyl points and opening a Dirac mass gap, evidenced by magnetoresistance and Hall effect measurements.

Contribution

It provides experimental evidence of a topological quantum phase transition driven by magnetic field in ZrTe5, revealing Weyl point annihilation and the emergence of a 2D Dirac mass gap.

Findings

Magnetic field of about 8 T induces Weyl point annihilation.

Sharp drop in magnetoresistance above 8 T linked to 2D Dirac gap.

Additional carriers observed via Hall effect and anisotropic magnetoresistance.

Abstract

Symmetry protected Dirac semimetals can be transformed into Weyl semimetals by breaking the protecting symmetry, leading to many exotic quantum phenomena such as chiral anomaly and anomalous Hall effect. Here we show that, due to the large Zeeman g factor and small band width along b-axis in Dirac semimetal ZrTe5, a magnetic field of about 8 T along b-axis direction may annihilate the Weyl points and open up a two-dimensional (2D) Dirac mass gap, when the Zeeman splitting exceeds the band width along b-axis. This is manifested by a sharp drop of magnetoresistance (MR) above 8 T, which is probably due to additional carriers induced by the orbital splitting of the zeroth Landau level associated with the 2D Dirac point, which is descendant of the original Weyl points. Further evidence of the additional carriers is provided by the Hall effect and different anisotropic magnetoresistance (AMR) in low and high field regions. Our experiment reveals a probable topological quantum phase transition of field induced Weyl points annihilation in Dirac semimetal ZrTe5 and gives an alternative explanation for the drop of MR at high field.