Observation of a semimetal–semiconductor phase transition in the intermetallic ZrTe₅

Abstract

The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly 1,2 in rel-ativistic field theory of chiral fermions (massless spin 1/2 particles with a definite projection of spin on momentum)-a dramatic phenomenon arising from a collective motion of particles and antiparti-cles in the Dirac sea. The recent discovery 3-5 of Dirac semimetals with chiral quasi-particles opens a fascinating possibility to study this phenomenon in condensed matter experiments. Here we report on the first observation of chiral magnetic effect through the measurement of magneto-transport in zirconium pentatelluride, ZrTe 5. Our angle-resolved photoemission spectroscopy experiments show that this material's electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. The observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background.

Pressure-induced superconductivity in a three-dimensional topological material ZrTe 5

“…In this paper, by combining multiple experimental probes (synchrotron X-ray diffraction, low-temperature transport under magnetic field) and theoretical investigations, we discover the pressure-induced 3D Dirac semimetal to superconductor transition in ZrTe 5 . semiconducting-like feature above 128 K, then the resistance decreases with the decrease of temperature followed by a slight upturn below 20 K. The large resistance anomaly around 128 K is quite similar to those observed under ambient pressure (12,15,30), and was generally correlated to the sign change of charge carriers although the origin still remains elusive (30). With increasing pressure, the peak temperature increases initially up to 150 K and then shifts back toward lower temperatures accompanied by the broadening of the peak and the decrease of the peak resistance.…”

Pressure-driven superconductivity in the transition-metal pentatellurideHfTe5

“…A similar resistive anomaly is observed in related zirconium pentatelluride ZrTe5 10,11 . This anomaly in pentatellurides is likely associated with peculiarities of their electronic structure although the origin still remains elusive 23,24,25 . Similarities in structure between the pentatellurides and chalcogenides strongly suggested the formation of a CDW as the origin of the resistivity anomalies.…”

Bipolar Conduction as the Possible Origin of the Electronic Transition in Pentatellurides: Metallic vs Semiconducting Behavior

“…In any case, possible causes for this behavior were advanced. These include density waves [3], inconsistent with the diffraction and high magnetic field data [4]; polaronic models [7], which are, however, apparently inconsistent with the good low-temperature conduction; a semimetal-semiconductor phase transition [8] or a temperature-induced Lifshitz transition [9,10]. More recently, these compounds have become of interest as topological materials whose low-energy electronic structure is controlled by spin-orbit interactions [11].…”