From surface Fermi arcs to Fermi loops in the Dirac semimetal Cd3As2

TL;DR

This study demonstrates the transition from surface Fermi arcs to Fermi loops in the Dirac semimetal Cd3As2 through experimental surface modifications and quantum oscillation measurements, revealing new topological surface state behaviors.

Contribution

It provides experimental evidence of Fermi arc to Fermi loop transition in Cd3As2, supporting the fragile topological nature of the material.

Findings

Surface modification increases spin polarization at higher gate voltages.

Quantum oscillations indicate the presence of Fermi loops.

Transition from Fermi arcs to Fermi loops confirmed by measurements.

Abstract

Arc-like topological surface states, i.e., surface Fermi arcs, have long been recognized as the hallmark of Dirac semimetals. However, recent theories suggest that the surface Fermi arcs could evolve into closed Fermi loops, akin to surface states in topological insulators, while preserving the bulk Dirac semimetal phase. Here we experimentally reveal the evolution of Fermi arcs to Fermi loops in the surface-modified Dirac semimetal Cd3As2 nanoplate through gate voltage-dependent spin transport and quantum oscillation measurements. Surface modification, achieved by heavy metal atom deposition and water molecule adsorption, leads to an increase in the current-induced spin polarization at higher gate voltages, contrasting with the decrease observed in the pristine nanoplate. We also observe surface Shubnikov-de Haas oscillations with frequencies that scale linearly with gate voltage, aligning with a Fermi loop scenario. These findings indicate a transition from Fermi arcs to a closed Fermi loop in the surface-modified Cd3As2 nanoplate, consistent with the theoretically predicted fragile topological nature of Cd3As2. Our research offers profound insights into the transitions among these subtle topological states in Dirac semimetals, paving the way for manipulating topological surface states for high-performance spintronic devices.