Topological semimetals without quasiparticles

TL;DR

This paper introduces a framework for understanding non-Fermi liquid topological phases in strongly correlated materials where quasiparticles are absent, revealing novel surface states and transport phenomena.

Contribution

It develops a symmetry-based approach to classify non-quasiparticle topological phases and demonstrates their realization in a specific lattice model with potential material candidates.

Findings

Identification of non-Fermi liquid topological phases with surface states

Demonstration of symmetry constraints on emergent excitations

Prediction of observable transport signatures like spin and valley Hall effects

Abstract

The interplay between interactions and topology in quantum materials is of extensive current interest. Strong correlations are known to be important for insulating topological states, as exemplified by the fractional quantum Hall effect. For the metallic case, whether and how they can drive topological states that have no free-electron counterparts is an open and pressing question. We introduce a general framework for lattice symmetries to constrain single-particle excitations even when they are not quasiparticles, and substantiate it in a periodic Anderson model with two channels of conduction electrons. We demonstrate that symmetry constrains correlation-induced emergent excitations to produce non-Fermi liquid topological phases. The loss of quasiparticles in these phases is manifested in a non-Fermi liquid form of spectral and transport properties, whereas its topological nature is characterized by surface states and valley and spin Hall conductivities. We also identify candidate materials to realize the proposed phases. Our work opens a door to a variety of non-Fermi liquid topological phases in a broad range of strongly correlated materials.