Role of Atomic Multiplets in the Electronic Structure of Rare-Earth Semiconductors and Semimetals

Abstract

We present a study of the effects of strong correlations in rare-earth pnictides, in which localized 4f states simultaneously retain atomiclike character and strongly influence the free-electron-like valence electron states. Using erbium arsenide as our example, we use a modern implementation of dynamical mean-field theory to obtain the atomic multiplet structure of the Er3+ 4f shell, as well as its unusually strong coupling to the electronic Fermi surfaces; these types of behavior are not correctly described within conventional electronic-structure methods. We are then able to explain the long-standing theoretical question of the quasisaturation of magnetization in an applied magnetic field, and to obtain the first quantitative agreement with experimental Shubnikov-de Haas frequencies of the Fermi-surface sheets.

Strong Electronic Correlations: Dynamical Mean-Field Theory and Beyond

“…4.5, we reproduce the LDA+U and LDA + DMFT bandstructures and density of states obtained in Ref. [37] for this material. This figure reveals important differences between the two methods, regarding the description of the localized f-states.…”

“…Under such circumstances, a simplified impurity solver can be used to solve the DMFT equations: in Ref. [37], the very simple Hubbard-I approximation was used, which consists in replacing the self-energy with that of the self-consistently embedded but isolated atom (hence, the self-consistent aspect only comes in through the total charge density and total electron number) [17]. In Fig.…”

Magnetism and electronic structure calculation of SmN

“…In order to consider the multiplet structure properly, an approach beyond the static mean-field is needed. The LDA+DMFT approach [33,34,35] in the Hubbard I approximation [35,36] is capable of capturing all these effects, and has already been applied to the paramagnetic ErAs [37], and to TbN [29]. This type of calculations introduce additional difficulties that we plan to address in our future research.…”

Size effects on the electronic structure of ErSb nanoparticles embedded in the GaSb(001) surface

“…While bulk Er-monopnictides ErP, ErAs, and ErSb are semimetals with Γ-X band overlap [16][17][18], basic quantum confinement models predict the opening of a band gap for ErAs thin films with thicknesses below 1.7 nm [11,19] and for ErAs nanoparticles with diameters less than 3 nm [12]. However, cross-sectional scanning tunneling spectroscopy measurements for ErAs nanoparticles showed no evidence of a gap, suggesting that simple hardwalled potential models are not sufficient to describe confined ErAs/GaAs structures [10,15].…”

“…After thermal desorption of the surface oxide under an As overpressure, a 200 nm GaAs buffer layer was grown at 540 °C, followed by a 200 nm GaSb layer at 500 °C. Both layers were doped with 1×10 18 Si atoms/cm 3 . The sample temperature was then ramped to the desired growth temperature for ErSb (between 400 -540 °C) and annealed with an Sb overpressure sufficient to maintain a strong c(2×6) reconstruction as observed by reflection high-energy electron diffraction (RHEED).…”