Electronic structure of low-carrier Yb 4 As 3 and related compounds (original) (raw)
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Physical Review B
Inelastic-neutron-scattering experiments on Yb 4 As 3 revealed the existence of low-energy spin excitations, which are characteristic of a one-dimensional Heisenberg-type antiferromagnetic coupling at low temperatures where charge ordering takes place. Superimposed on the one-dimensional spin excitations, an unusual magnetic response is also observed around the one-dimensional zone center. These results strongly suggest that the heavy-electron behavior in Yb 4 As 3 is a unique phenomenon caused by charge ordering; it results from the fact that the compound contains doped one-dimensional 4 f 1 hole chains with strong on-site f-electron correlations.
Physical Review B, 2000
Electron paramagnetic resonance ͑EPR͒, optical absorption, fluorescence, and excitation spectra of CsCdBr 3 :1% Yb 3ϩ single crystals were taken at 4.2 K. An analysis of the dependence of the EPR spectrum on the magnetic-field direction and a comparison of the recorded signal shapes with simulated envelopes over the magnetic dipole transitions of the expected dimers containing all ytterbium isotopes were performed. This allowed us to assign the measured EPR spectra unambiguously to the symmetrical pair center of the type Yb 3ϩ -Cd 2ϩ vacancy-Yb 3ϩ substituting for three adjacent Cd 2ϩ ions in the bromine octahedra chains. A distance of 0.596 nm between the magnetically equivalent Yb 3ϩ ions was determined from the line splitting due to magnetic dipole-dipole interaction. An interpretation of the optical spectra in compounds containing ͑YbBr 6 ͒ 3Ϫ complexes is presented, which is based on a crystal-field theory accounting for an interaction between the ground 4 f 13 (Yb 3ϩ )͓4p 6 (Br Ϫ )͔ 6 and excited 4 f 14 (Yb 2ϩ )4p 5 (Br)͓4p 6 (Br Ϫ )͔ 5 charge-transfer configurations. The observed large splitting of the excited 2 F 5/2 (4 f 13 ) crystal-field multiplet is explained on the basis of a quasiresonant hybridization of the 4 f -hole state with the spin orbitals of the charge-transfer states. With physically reasonable values of the fitted model parameters, the calculated energy level diagram of the 4 f 13 configuration and the g tensor of the Yb 3ϩ ion in the crystal-field ground state are in good agreement with the experimental data.
Electronic structure of YbTX compounds
Journal of Alloys and Compounds, 2003
The electronic structure of ternary YbTX compounds (T5Au, Pd, Rh, Pt; X5Sn, Bi) was studied by X-ray photoemission spectroscopy (XPS). XPS valence bands were compared with calculations using the tight-binding linear muffin-tin orbital method. The results showed that the valence bands in these compounds were formed mainly by the 4f orbitals of ytterbium and the 4d (5d) orbitals of the transition elements. Analysis of the Yb 4f valence band and Yb 4d core level states clearly indicated the presence of divalent Yb ions in YbAuSn and YbAuBi, and trivalent ions in YbRhSn and YbPtSn. In turn, the Yb ions in YbPdBi exhibited a mixed valence character.
ACS Omega, 2019
This work presents an electronic structure study employing multireference configuration interaction MRCI calculations with Davidson correction (+Q) of the ytterbium monobromide YbBr molecule. Adiabatic potential energy curves (PECs), dipole moment curves, and spectroscopic constants (such as R e , ω e , B e , D e , T e , and μ e) of the lowlying bound electronic states are determined. The ionic character of the YbBr molecule at the equilibrium position is also discussed. With spin−orbit effects, 30 low-lying states in Ω = 1/2, 3/2, 5/2, 7/2 representation are probed. The electronic transition dipole moment is calculated between the investigated states and then used to determine transition coefficients, for example, the Einstein coefficient of spontaneous emission A ij and emission oscillator strength f ij. Vibrational parameters such as E ν , B ν , D ν , R min , and R max of the low vibrational levels of different bound states in both Λ and Ω representations are also calculated. Upon calculating the Franck−Condon factors, they are found to be perfectly diagonal between three couples of low-lying excited states. Vibrational Einstein coefficients and radiative lifetimes are computed as well for the lowest vibrational transitions. Most of the data reported in this work are presented here for the first time in the literature. Very good accordance is obtained in comparison with the previously reported constants by means of experimental methods.
Temperature-invariant valence-band 4f photoemission features in the heavy-fermion compound YbAl3
Physical Review B - PHYS REV B, 1993
A high-resolution photoemission (PES) study of the heavy-fermion compound YbAl3 has been undertaken to test the qualitative and quantitative predictions of the single-impurity model. Corroborating data on YbAgCu4 and YbCu2Si2 are also presented. For Yb-based heavy fermions the model predicts a fully occupied Kondo resonance so that its width, intensity, and temperature dependence should be directly accessible by PES. Due to the existence of temperature- and/or contamination-dependent surface features, which are not dealt with by the model, a rigorous normalization and curve-fitting procedure was required to extract the bulk 4f line shape. For the particular temperature cycling method employed by us, we do not observe any temperature dependence in the peak that had been previously identified as the Kondo resonance. We find that both the binding energy and width of this peak are significantly larger than theory predicts. It is also found that the trends in 4f line shape and surface sh...
Electronic structure and magnetic ordering of the unconventional antiferromagnet Yb 3 Pt 4
EPL (Europhysics Letters), 2009
PACS 71.20.-b -Electron density of states and band structure of crystalline solids PACS 71.27.+a -Strongly correlated electron systems; heavy fermions PACS 75.20.Hr -Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions Abstract -Applying density functional theory within the generalized gradient approximation, we investigate the electronic and magnetic properties of the intermetallic rare-earth system Yb3Pt4. This material recently has been put forward as host for quantum criticality, while details of the magnetic ordering could not be established (Bennett N. C. et al., J. Magn. & Magn. Mater., 321 (2009) 2021). In this context, we investigate the effect of spin-orbit coupling and compare various spin patterns from the energetic point of view, which enables us to determine the electronic ground state of Yb3Pt4. The assumption of an elementary superexchange mechanism yields a magneticcoupling constant in good agreement with the experimental ordering temperature.
Non-Kondo-like Electronic Structure in the Correlated Rare-Earth Hexaboride YbB_{6}
Physical review letters, 2015
We present angle-resolved photoemission studies on the rare-earth-hexaboride YbB_{6}, which has recently been predicted to be a topological Kondo insulator. Our data do not agree with the prediction and instead show that YbB_{6} exhibits a novel topological insulator state in the absence of a Kondo mechanism. We find that the Fermi level electronic structure of YbB_{6} has three 2D Dirac cone like surface states enclosing the Kramers's points, while the f orbital that would be relevant for the Kondo mechanism is ∼1 eV below the Fermi level. Our first-principles calculation shows that the topological state that we observe in YbB_{6} is due to an inversion between Yb d and B p bands. These experimental and theoretical results provide a new approach for realizing novel correlated topological insulator states in rare-earth materials.
International Journal of Quantum Chemistry
We present a comprehensive theoretical study of the electronic structures of the Yb atom and the Yb 2 molecule, respectively, focusing on their ground and lowestlying electronically excited states. Our study includes various state-of-the-art quantum chemistry methods such as CCSD, CCSD(T), CASPT2 (including spin-orbit coupling), and EOM-CCSD as well as some recently developed pCCD-based approaches and their extensions to target excited states. Specifically, we scan the lowest-lying potential energy surfaces of the Yb 2 dimer and provide a reliable benchmark set of spectroscopic parameters including optimal bond lengths, vibrational frequencies, potential energy depths, and adiabatic excitation energies. Our in-depth analysis unravels the complex nature of the electronic spectrum of Yb 2 , which is difficult to model accurately by any conventional quantum chemistry method. Finally, we scrutinize the bi-excited character of the first 1 Σ + g excited state and its evolution along the potential energy surface.
Solid State Communications, 1992
We report high-resolution photoemission results for the 4f levels in YbCu2Si2 and CeSi2. The data are compared to the predictions of the Anderson impurity model for valence band photoemission. These predicted spectra are obtained both in an approximate fashion by broadening crystal field (CF) states whose parameters are determined from existing neutron scattering data, as well as from a Gunnarson-Schonhammer calculation. Inclusion of crystal fields does not affect our two fundamental conclusions: that there is a natural linewidth in the problem (~-130meV) which is much greater than predicted by the Anderson model, and that the expected temperature dependence of the Kondo resonance is absent. Due to the large natural linewidth, experimental resolution (60-95meV) is not a limiting factor.