Quantum Hall effects in a Weyl semimetal: Possible application in pyrochlore iridates

TLDR

Pyrochlore iridates A₂Ir₂O₇ attract interest because they combine strong spin–orbit coupling and strong correlations, and their Weyl semimetallic state has zero carrier density, reaching the quantum limit even in weak magnetic fields. The paper investigates two novel magnetic‑field–induced quantum effects in the Weyl semimetal: a pressure‑induced anomalous Hall effect and a charge‑density wave pinned at the wavevector linking opposite‑chirality Weyl nodes. The authors derive a general formula for the anomalous Hall coefficient in a Weyl semimetal and analyze the pressure‑induced anomalous Hall effect and the field‑induced charge‑density wave at the Weyl‑node‑connecting wavevector. LDA calculations indicate that A₂Ir₂O₇ is a three‑dimensional Weyl semimetal, and the predicted anomalous Hall and charge‑density‑wave.

Abstract

There have been lots of interest in pyrochlore Iridates A2Ir2O7 where both strong spin-orbital coupling and strong correlation are present. A recent LDA calculation suggests that the system is likely in a novel three dimensional topological semi-metallic phase: a Weyl semi-metal. Such a system has zero carrier density and arrives at the quantum limit even in a weak magnetic field. In this paper we discuss two novel quantum effects of this system in a magnetic field: a pressure-induced anomalous Hall effect and a magnetic field induced charge density wave at the pinned wavevector connecting Weyl nodes with opposite chiralities. A general formula of the anomalous hall coefficients in a Weyl semi-metal is also given. Both proposed effects can be probed by experiments in the near future, and can be used to detect the Weyl semi-metal phase.