Surface States and Arcless Angles in Twisted Weyl Semimetals

TL;DR

This paper explores how twisting Weyl semimetal surfaces alters Fermi arc states, leading to the emergence of interface-bound states and the disappearance of Fermi arcs at special angles, with implications for magneto-oscillations and optical responses.

Contribution

It introduces the concept of arcless angles in twisted Weyl semimetals where Fermi arcs vanish and interface states form, revealing new topological phenomena.

Findings

Fermi arcs can be suppressed at specific twist angles.

Interface states form as Fermi loops when arcs are absent.

Resonance signatures appear in optical conductivity under magnetic fields.

Abstract

Fermi arc states are features of Weyl semimetal (WSM) surfaces which are robust due to the topological character of the bulk band structure. We demonstrate that Fermi arcs may undergo profound restructurings when surfaces of different systems with a well-defined twist angle are tunnel-coupled. The twisted WSM interface supports a moir\'e pattern which may be approximated as a periodic system with large real-space unit cell. States bound to the interface emerge, with interesting consequences for the magneto-oscillations expected when a magnetic field is applied perpendicular to the system surfaces. As the twist angle passes through special "arcless angles', for which open Fermi arc states are absent at the interface, Fermi loops of states confined to the interface may break off, without connecting to bulk states of the WSM. We argue that such states have interesting resonance signatures in the optical conductivity of the system in a magnetic field perpendicular to the interface.