Weyl Mott Insulator

TL;DR

This paper introduces the Weyl Mott insulator, a novel topological phase where electron-electron interactions induce a Mott gap in Weyl fermions, resulting in unique spectral and transport properties.

Contribution

It theoretically demonstrates that interactions can open a Mott gap in Weyl fermions without destroying their topological nature, leading to the concept of a Weyl Mott insulator.

Findings

Weyl Mott insulator exhibits energy gaps in ARPES and optical conductivity.

It maintains a nonzero Hall conductance despite the gap.

Surface Fermi arcs with diverging penetration depth are predicted.

Abstract

Relativistic Weyl fermion (WF) often appears in the band structure of three dimensional magnetic materials and acts as a source or sink of the Berry curvature, i.e., the (anti-)monopole. It has been believed that the WFs are stable due to their topological indices except when two Weyl fermions of opposite chiralities annihilate pairwise. Here, we theoretically show for a model including the electron-electron interaction that the Mott gap opens for each WF without violating the topological stability, leading to a topological Mott insulator dubbed {\it Weyl Mott insulator } (WMI). This WMI is characterized by several novel features such as (i) energy gaps in the angle-resolved photo-emission spectroscopy (ARPES) and the optical conductivity, (ii) the nonvanishing Hall conductance, and (iii) the Fermi arc on the surface with the penetration depth diverging as approaching to the momentum at which the Weyl point is projected. Experimental detection of the WMI by distinguishing from conventional Mott insulators is discussed with possible relevance to pyrochlore iridates.