Large Fermi surface expansion through anisotropic mixing of conduction and f electrons in the semimetallic Kondo lattice CeBi

Abstract

Using angle-resolved photoemission spectroscopy (ARPES) and resonant ARPES, we report evidence of strong anisotropic conduction-f electron mixing (c-f mixing) in CeBi by observing a largely expanded Ce-5d pocket at low temperature, with no change in the Bi-6p bands. The Fermi surface (FS) expansion is accompanied by a pronounced spectral weight transfer from the local 4f 0 peak of Ce (corresponding to Ce 3+ ) to the itinerant conduction bands near the Fermi level. Careful analysis suggests that the observed large FS change (with a volume expansion of the electron pocket up to 40%) can most naturally be explained by a small valence change (~ 1%) of Ce, which coexists with a very weak Kondo screening. Our work therefore provides evidence for a FS change driven by real charge fluctuations deep in the Kondo limit, which is made possible by the low carrier density.

Photo-emission signatures of coherence breakdown in Kondo alloys: dynamical mean-field theory approach

“…For all values considered for the Kondo interaction and the electronic filling, we find that the Fermi surface of the Kondo lattice (x = 1) is large and it includes the contributions from both the conduction electrons and the Kondo spins. This universal feature is in good agreement with previous theoretical and experimental results [52,53,54,55,56,57,58,59,60,61,62]. It can be well understood in terms of Luttinger theorem, which stipulates that all fermionic degrees of freedom participate in the formation of the Fermi liquid ground state.…”

“…For example, PES experiments revealed limitations of the single impurity models for describing dense Kondo systems [36,37,38]. ARPES experiments carried on varieties of Kondo lattice systems like CeRu 2 Si 2 [54,55,56], CeRu 2 Ge 2 [57], CeBi [58],CeNiSn [59] and YbRh 2 Si 2 [60,61,62] showed large Fermi surfaces due to the coherent participation of 4f electrons. ARPES experiments also permitted a direct observation of dispersive Kondo resonance peaks in CeCoGe 1.2 Si 0.8 [63] and surface and bulk hybridizations in antiferromagnetic Kondo lattice CeRh 2 Si 2 [64].…”

Direct evidence of electron-hole compensation for XMR in topologically trivial YBi

“…The spin-orbit coupling (SOC) effect was included in all calculations. The mBJ method could overcome the band gap underestimation and band inversion overestimation using the PBE method [11,12,29,34,36,38,44,45], which was also verified by our experimental results. Therefore, unless specifically indicated, the calculation results in this work were obtained using the mBJ method.…”

“…Because angle resolved photoemission spectroscopy (ARPES) has the ability to directly reveal the band structures of materials, the band topologies of numerous RPn compounds have been experimentally studied [11-13, 25-27, 30-38]. Topological band inversion and nontrivial surface states were observed in compounds with group VI element Bi, such as LaBi [13,[30][31][32][33], SmBi [26,36], and CeBi [36][37][38], while compounds with other group VI elements were confirmed to be topologically trivial without band inversion [11, 12, 25-27, 34, 35, 37]. In those topologically trivial compounds, XMR behaviours are widely attributed to the classical electron-hole carrier compensation scenario [11,12].…”

Charge density wave and weak Kondo effect in a Dirac semimetal CeSbTe

“…The on-resonant spectrum featured two broad 4f peaks, one at −3.2 eV and the other at −0.7 eV. The deep energy peak (−3.2 eV) can be attributed to the localized 4f peak (4f 0 ), whose energy is deeper than most Kondo systems (typically between −3 and −2 eV), including prototypical low carrier density Kondo systems such as CeSb and CeBi [52,53]. Based on the single impurity Anderson model, a deeper 4f 0 peak reflects the more localized nature of 4f electrons [51].…”