Electronic structure of metallic tetra-boride $\textrm{TmB}_{\textrm{4}}$: An LDA+DMFT study

TL;DR

This study investigates the electronic structure and strong correlation effects in the metallic tetraboride TmB4 using advanced theoretical methods, revealing non-Fermi liquid behavior and the impact of spin-orbit coupling on its Fermi surface.

Contribution

It applies LDA+DMFT with MO-IPT to analyze TmB4, highlighting the role of strong correlations, spin-orbit coupling, and geometric frustration in its electronic properties.

Findings

Pseudo-gap behavior in spectral function

Non-Fermi liquid self-energy behavior

Fermi surface topology changes with SOC

Abstract

Recent experimental observations of magnetization plateau in metallic tetraboride $\textrm{TmB}_{4}$ have created a lot of interest in these class of materials. Hysteretic longitudinal resistance and anomalous Hall Effect are other remarkable features in the rare-earth tetraborides which represent experimental realizations of Archimedean Shastry-Sutherland (SSL) lattice. Electronic band structures, calculated under GGA and GGA+SO approximations, show that $\textrm{TmB}_{4}$ is a narrow band system with considerable correlation in its f-level. Strong correlation effects in this system are studied under single-site dynamical mean field theory (DMFT) [LDA+DMFT scheme] using multi-orbital generalization of iterated perturbation theory (MO-IPT). Pseudo-gap behaviour in spectral function and non-Fermi liquid behaviour of self-energy shows non-trivial strong correlation effects present in this geometrically frustrated metallic magnets. We also consider the extant, heather-to-neglected, strong atomic spin-orbit coupling (SOC) effects. While there is a significant change in the topology of the Fermi surface in the presence of SOC, the non-Fermi liquid behavior survives. The system can be modelled by an effective two orbital spinless Falicov-Kimball model together with two free band like states.