Spin-polarized imaging of strongly interacting fermions in the ferrimagnetic state of Weyl candidate CeBi

TL;DR

This study combines theoretical calculations and advanced microscopy to reveal how hybridization between Bi p states and Ce f states in CeBi leads to strong interactions and band renormalization in its ferrimagnetic Weyl semimetal phase.

Contribution

It provides the first direct imaging of surface ferrimagnetic order and demonstrates the role of p-f hybridization in band renormalization in CeBi's Weyl phase.

Findings

Observation of surface ferrimagnetic order via spin-polarized STM

Detection of Bi p states partially Kondo screened by Ce f moments

Confirmation of band flattening and splitting consistent with DFT and QPI

Abstract

CeBi has an intricate magnetic phase diagram whose fully-polarized state has recently been suggested as a Weyl semimetal, though the role of $f$ states in promoting strong interactions has remained elusive. Here we focus on the less-studied, but also time-reversal symmetry-breaking ferrimagnetic phase of CeBi, where our density functional theory (DFT) calculations predict additional Weyl nodes near the Fermi level $E_\mathrm{F}$. We use spin-polarized scanning tunneling microscopy and spectroscopy to image the surface ferrimagnetic order on the itinerant Bi $p$ states, indicating their orbital hybridization with localized Ce $f$ states. We observe suppression of this spin-polarized signature at $E_\mathrm{F}$, coincident with a Fano line shape in the conductance spectra, suggesting the Bi $p$ states partially Kondo screen the $f$ magnetic moments, and this $p-f$ hybridization causes strong Fermi-level band renormalization. The $p$ band flattening is supported by our quasiparticle interference (QPI) measurements, which also show band splitting in agreement with DFT, painting a consistent picture of a strongly interacting magnetic Weyl semimetal.