Uncovering surface states of the Dirac semimetal BaMg2Bi2

TL;DR

This study combines high-resolution ARPES and DFT calculations to reveal and analyze the surface states of BaMg2Bi2, a Dirac semimetal, clarifying its electronic structure and resolving previous experimental-theoretical discrepancies.

Contribution

It provides the first detailed experimental observation of surface states in BaMg2Bi2 and clarifies their topological triviality, enhancing understanding of its electronic properties.

Findings

Identification of previously unobserved surface states

Surface states are topologically trivial

Reconciliation of experimental data with theoretical models

Abstract

BaMg2Bi2 is a Dirac semimetal characterized by a simple Dirac cone crossing the Fermi level at the center of the Brillouin zone, protected by C3 rotational symmetry. Together with its Sr-based analogue SrMg2Bi2, it has been proposed as a promising candidate for a chemically driven topological switch: while SrMg2Bi2 is an insulator, BaMg2Bi2 exhibits non-trivial topological features. A detailed understanding of its electronic structure is essential to elucidate its electronic and transport properties. Previous photoemission studies confirmed the Dirac nature of BaMg2Bi2, but were limited to high photon energies, which hindered direct comparison with density functional theory calculations (DFT), due to reduced resolution and higher-frequency matrix-element modulation in that regime. In this work, we combine high-resolution angle-resolved photoemission spectroscopy (ARPES) and DFT calculations to get full insight on the valence band states, providing a comprehensive picture of the low-energy electronic structure. Our measurements reveal the presence of previously unobserved surface states. We found that they are topologically trivial, but they unlock a more comprehensive understanding of the material's behavior, reconciling previous discrepancies between experiment and theory.