Observation of a kink in the dispersion of f-electrons

Abstract

Strong interactions in correlated electron systems may result in the formation of heavy quasiparticles that exhibit kinks in their dispersion relation. Spectral weight is incoherently shifted away from the Fermi energy, but Luttinger's theorem requires the Fermi volume to remain constant. Our angle-resolved photoemission study of USb2 reveals a kink in a noncrossing 5f band, representing the first experimental observation of a kink structure in f -electron systems. The kink energy scale of 21 meV and the ultra-small peak width of 3 meV are observed. We propose the novel mechanism of renormalization of a point-like Fermi surface, and that Luttinger's theorem remains applicable.

Quest for Band Renormalization and Self-Energy in Correlated f-Electron Systems

“…3 was proposed [5,6] to explain the experimental findings in agreement with the results of the many-body calculations, which revealed a quadratically dispersing, narrow and coherent quasiparticle width for small values of momentum. The effective mass for small k is twice larger than seen for larger values of k, and the crossover region between two different dispersion rates is formed, manifesting itself as a kink (Fig.…”

“…Building on our previous experience with USb 2 [13], in 2008 we have discovered a small energy scale in this compound via the observation of a kink in f -electron dispersion [5,6], see Fig. 1, panel B.…”

“…A great body of work has been devoted to the extraction of the self-energy from kinks observed in the band dispersion measured with angle resolved photoemission (ARPES) having a high energy and momentum resolution. The effort of transcribing the experimental tools developed for high temperature superconductors onto the area of f -electrons was initiated at Los Alamos National Laboratory (LANL) most recently [5,6]. This initial work reveals that a finite value of the real part of self-energy exists and can be measured in f -electron systems.…”

Photoemission investigations of URu2Si2

“…Finally, the focus of all the recent high-resolution ARPES work was the vicinity of E f , where the Fermi surface is located. But, from the point of view of band renormalization, kinks in band dispersion associated with increased real part of self-energy can appear both at low energies of the order of 10 meV [49], and -especially if driven by magnetic fluctuations -at high energies of the order of 1 eV [50]. Since spin fluctuations are emerging as a dominant actor responsible for gapping [48], it would be a natural next step to search for high energy features in the spectral function.…”

Measurement of Two Low-Temperature Energy Gaps in the Electronic Structure of AntiferromagneticUSb2Using Ultrafast Optical Spectroscopy

“…Antiferromagnetic USb 2 (T N $ 203 K) [6,7] is an excellent candidate for exploring these issues, as it is a moderately correlated electron system with a quasi-2D electronic structure exhibiting characteristics of both localized and itinerant 5f electrons [8][9][10][11][12][13]. Moreover, previous angleresolved photoemission spectroscopy (ARPES) studies [13,14] produced the first measurements of the self-energy in 5f electron systems and a model of boson-mediated band renormalization [15].…”