Viewed as three-dimensional (3D) analogue of graphene and with linear energy dispersion in bulk, Dirac semimetals have been widely studied recently due to their potential impact on information technology. Several materials such as Cd₃As₂ are predicated to be Dirac semimetal, while most of them are not layered materials which are hard for Nano device fabrication and further application.

The layered material ZrTe₅ has been demonstrated to be a Dirac semimetal, according to recent ARPES and magneto-infrared spectroscopy experiments. While a direct transport evidence for Dirac semimetal phase in ZrTe₅ is still lacking, especially the observation of the nontrivial Berry phase in this material. Using the Steady High Magnetic Field Facilities (SHMFF) with a magnetic field up to 31 T and temperature down to 0.3 K, the group led by TIAN Mingliang, High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL), carries out a detailed transport study on ZrTe₅ nanoribbons and gives a clear transport evidence for Dirac semimetal phase in ZrTe₅.

In this work, a negative magnetoresistance (NMR) is discovered while the magnetic field is parallel to the current. Tilting the magnetic field away from the current direction, the NMR is sharply suppressed. Changing the current direction, the NMR can also be identified while magnetic field is parallel to the current. Such an NMR is called “chiral magnetic effect”----the hallmark of 3D Dirac semimetal. Besides, a strong quantum oscillation is revealed in this material and a nontrivial Berry phase is demonstrated after a detailed analysis of the quantum oscillation. A clear Landau level splitting is also demonstrated in ZrTe₅ under high magnetic field, revealing a possible transformation of ZrTe₅ from 3D Dirac semimetal to Weyl semimetal by breaking the time reversal symmetry.

This work has been published on Phys. Rev. B 93, 115414 (2016), with the title “Transport evidence for three-dimensional Dirac semimetal phase in ZrTe5”.