Metallic layered materials with magnetic frustration: An ARPES view of the SmAuAl$_4$Ge$_2$ and TbAuAl$_4$Ge$_2$

TL;DR

This study uses ARPES and DFT to explore the electronic structure of SmAuAl$_4$Ge$_2$ and TbAuAl$_4$Ge$_2$, revealing effects of localized spins, surface states, and the influence of low-dimensionality, exchange, and spin-orbit coupling.

Contribution

First experimental electronic structure analysis of LnTAl$_4$X$_2$ compounds using ARPES and DFT, highlighting the role of localized spins and surface states.

Findings

Identification of surface-localized electronic states

Observation of the influence of localized spin moments on electronic structure

Revealing the importance of low-dimensionality, exchange, and spin-orbit coupling

Abstract

Compounds of the new materials class LnTAl$_4$X$_2$ (Ln = lanthanide, X = tetrel, T = transition metal) host exotic magnetic phenomena due to geometric frustration induced by their triangular lattice. Complex spin arrangements, magnetic fluctuations and double magnetic transitions have been well observed by means of magneto-transport. Nevertheless, the experimental electronic structure of this family of materials has been poorly studied. We have investigated the experimental electronic structure of two members of this class of materials: SmAuAl$_4$Ge$_2$ and TbAuAl$_4$Ge$_2$. By means of Angle-Resolved PhotoEmission Spectroscopy (ARPES) accompanied by Density Functional Theory calculations (DFT), we reveal common trends and features, the important effect of localized spin moments on the electronic structure, the presence of surface-localized electronic states and the nature of the surface termination layer. Low-dimensionality, exchange interaction, and spin-orbit coupling are all important ingredients of the electronic structure.