Scientists from High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL) observed disruption of accidental Dirac semimetal state in ZrTe₅ under hydrostatic pressure.

The layered compound zirconium pentatelluride had been studied for decades due to its large thermoelectric power, mysterious resistivity anomaly, and large positive magnetoresistance (MR).

Very recently, it was predicted that the single-layer ZrTe₅ is a candidate for a large-gap quantum spin Hall insulator and the 3D bulk crystal is either a weak or a strong topological insulator. Experimental verification, on the other hand, remains highly controversial.

Scanning tunneling microscopy or spectroscopy (STM/STS) and angle-resolved photoemission spectroscopy (ARPES) measurements indicate it is a topological insulator. In contrast, the magnetotransport measurements support the scenario of 3D Dirac semimetal.

As applying pressure is known to be a powerful approach to tune electronic states and lattice structures without disorder or impurity, researchers at CHMFL studied the effect of hydrostatic pressure on the magnetotransport properties of ZrTe₅.

They observed that, in the case of H||b, the MR decreases drastically with applying pressure.

Besides, the change of the quantum oscillation phase was revealed around 2GPa, those results suggest the pressure breaks the "accidental" Dirac node in ZrTe₅.

While for H||c, both the quantum oscillations and MR are robust against pressure. Combining with the studies in different field orientations, they found that ZrTe₅ evolves from a highly anisotropic to a nearly isotropic electronic system in the presence of pressure, which accompanies the disruption of the "accidental" Dirac semimetal state.

It supports the assumption that ZrTe₅ is a semi-3D Dirac system with linear dispersion along two directions and a quadratic one along the third.

The results had published in Physical Review Letters with the title "Disruption of the Accidental Dirac Semimetal State in ZrTe₅ under Hydrostatic Pressure".

This work was supported by the Natural Science Foundation of China, and the Natural Science Foundation of Anhui province, the program of Users with Excellence, the Hefei Science Center of CAS.

The magnetoresistance and quantum oscillations of ZrTe₅ at various pressures. (a) The magnetoresistance of ZrTe₅ at various pressures (b) Shubnikov–de Haas oscillations component ΔR as a function of inverse magnetic field taken at different pressures. (c) Pressure dependence of the quantum oscillation frequency (Fermi surface size) and the effective mass. (d) Landau level index plots of the oscillations at various pressures. (Image by ZHANG Jinglei)