Quantum Oscillations at Integer and Fractional Landau Level Indices in ZrTe5

TL;DR

This study reveals quantum oscillations at fractional Landau levels in ZrTe5, indicating strong electron-electron interactions in this 3D Dirac semimetal, with implications for understanding quantum phenomena in topological materials.

Contribution

First observation of fractional Landau level oscillations in ZrTe5, demonstrating strong electron-electron interactions in a 3D Dirac semimetal.

Findings

Observation of quantum oscillations at fractional Landau levels N=2/3 and 2/5

Detection of non-trivial Berry's phase of π from Landau level fan diagram

Anomalous Hall effect-like behavior near zero magnetic field

Abstract

A three-dimensional (3D) Dirac semimetal (DS) is an analogue of graphene, but with linear energy dispersion in all (three) momentum directions.3D DSs have been a fertile playground in discovering novel quantum particles, for example Weyl fermions, in solid state systems.Many 3D DSs (e.g., ZrTe5) were theoretically predicted. We report here the results from the studies of aberration-corrected scanning transmission electron microscopy and low temperature magneto-transport measurements in exfoliated ZrTe5 thin flakes.Several unique results were observed. First, an anomalous-Hall-effect-like behavior was observed around zero magnetic field (B).Second, a non-trivial Berry's phase of \pi\ was obtained from the Landau level fan diagram of the Shubnikov-de Haas oscillations in the longitudinal resistivity. Third, the longitudinal resistivity shows linear B field dependence in the quantum limit. Most surprisingly, quantum oscillations were observed at fractional Landau level indices N = 2/3 and 2/5, demonstrating strong electron-electron interactions effects in ZrTe5.