Spanning Fermi arcs in a two-dimensional magnet

TL;DR

This paper demonstrates the creation and control of giant open Fermi arcs on the surface of ultrathin hybrid magnets, revealing a new interplay between magnetism and topological surface states with potential transport implications.

Contribution

It introduces a novel system where magnetism and topology interact, enabling control over Fermi arc shape and position through magnetization tuning in a two-dimensional magnet.

Findings

Giant open Fermi arcs are observed on ultrathin hybrid magnets.

Fermi surface topology is significantly altered by hybridization with a heavy-metal substrate.

Fermi arcs can be controlled by changing the magnetization direction.

Abstract

The discovery of topological states of matter has led to a revolution in materials research. When external or intrinsic parameters break certain symmetries, global properties of topological materials change drastically. A paramount example is the emergence of Weyl nodes under broken inversion symmetry, acting like magnetic monopoles in momentum space. However, while a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive due to both considerable experimental and theoretical challenges. Here, we demonstrate that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets. The Fermi-surface topology of an atomically thin ferromagnet is substantially modified by the hybridization with a heavy-metal substrate, giving rise to Fermi-surface discontinuities that are bridged by the Fermi arcs. Due to the interplay between magnetism and topology, we can control both the shape and the location of the Fermi arcs by tuning the magnetization direction. The hybridization points in the Fermi surface can be attributed to a non-trivial "mixed" topology and induce hot spots in the Berry curvature, dominating spin and charge transport as well as magneto-electric coupling effects.