The first-principles research on the role of surface in the heavy fermion compound CeRh$_2$Si$_2$

TL;DR

This study uses first-principles calculations to explore how surface effects influence the electronic structure of CeRh$_2$Si$_2$, revealing significant modifications to Kondo resonance and band structures that align with experimental observations.

Contribution

It provides a detailed first-principles analysis of surface effects on heavy fermion CeRh$_2$Si$_2$, highlighting their importance in strongly correlated materials.

Findings

Surface relaxation alters Fermi level and band dispersion.

Reduced hybridization weakens Kondo resonance at the surface.

Surface electric field modifies Kondo peak splitting and Hubbard bands.

Abstract

In the heavy fermion materials, the characteristic energy scales of many exotic strongly correlated phenomena (Kondo effect, magnetic order, superconductivity, etc.) are at milli-electron-volt order, implying that the heavy fermion materials are surface sensitive. Here, we investigate the electronic structures for Si- and Ce-terminated surfaces of CeRh$_2$Si$_2$ by first-principles methods. Our research reveals three notable impacts of surface effects on electronic structures, which are consistent with recent angle-resolved photoemission spectroscopy (ARPES) experiments. Firstly, the relaxation of surface crystal structures changes the relative position of Fermi level, adjusts the dispersion of bands and enhances the Kondo resonance. Secondly, the decrease of the hybridization between the Ce-4$f$ and conduction electrons in the surface layer leads to a weaker Kondo resonance peak and the shift of spin-orbit bands. Thirdly, the variation of crystal electric field around surface Ce atoms affects the splitting of Kondo resonance peaks, and also pushes down the lower-Hubbard bands of surface 4$f$ electrons. Moreover, we find the characteristic of bulk's lower-Hubbard bands, which was overlooked in previous works. Our investigation suggests that these surface effects are potentially important and highlighted in the future researches on properties of strongly correlated materials.