Electronic structure of rare-earth hexaborides

Abstract

Reflectivity spectra of all rare-earth hexaboride RB6 I', R =La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, and Y) single crystals have been measured systematically in the energy region from 1 meV to 40 eV at 300 K in order to investigate the electronic state and the contribution of the 4f electron to the band structure. The analysis of the optical conductivity and the loss-function spectra, which were derived from the Kramers-Kronig transformation of the reflectivity spectra, allowed us to make clear the origin of the peak structure in the spectrum due to the various interband transitions. The origins of the main peaks in the spectrum were assigned to the interband transitions from the bonding to the antibonding bands of the boron Zs and 2p states and to the rare-earth 5d state. The intra-atomic transition from the 4f and the Sp to the Sd(tzs ) states in the rare-earth ion was also observed.

Study on the electronic structure and the optical performance of YB6 by the first-principles calculations

“…3 with Fig. 4(b), we can conclude that the plasma frequency of YB 6 is 1.71 eV, and the calculated curve is in good agreement with the available loss-function spectra 7 indicated by the dotted line. It should be mentioned here that the available loss-function spectra was obtained from the Kramers-Kroning transformation of the relevant experimental reflectivity spectrum.…”

“…It appears that yttrium hexaboride (YB 6 ), belonging to a series of extremely hard, refractory, and stable rare-earth hexaborides, 5 is also to be applied as solar radiation shielding material for windows, because it resembles LaB 6 in many physical properties, such as the energy band structure 6 and the reflectivity spectra. 7,8 To our knowledge, a lot of researchers have extensively studied YB 6 , focusing their attention on its super-conductivity, 9-12 thermoelectricity, 13 and optical performance. 7,8 However, there have been no detailed theoretical studies concerning the electronic structure and the optical performance of YB 6 up to now, though Kimura et al 7,8 once measured the reflectivity spectra of YB 6 at 300 K and 9 K in a wide range from 1 meV to 40 eV through synchrotron radiation (SR), and they obtained the principal optical conductivity spectra and the loss-function spectra through the Kramers-Kronig relation.…”

“…7,8 To our knowledge, a lot of researchers have extensively studied YB 6 , focusing their attention on its super-conductivity, 9-12 thermoelectricity, 13 and optical performance. 7,8 However, there have been no detailed theoretical studies concerning the electronic structure and the optical performance of YB 6 up to now, though Kimura et al 7,8 once measured the reflectivity spectra of YB 6 at 300 K and 9 K in a wide range from 1 meV to 40 eV through synchrotron radiation (SR), and they obtained the principal optical conductivity spectra and the loss-function spectra through the Kramers-Kronig relation. Thus, we are inspired to study the electronic structure and the optical performance of YB 6 resorting to first-principles calculations in this paper.…”

Electronic and optical properties of ZrB12 and YB6. Discussion on electron‐phonon coupling

“…3 Electronic band structure and optical conductivity The calculation of band structure has already been reported for ZrB 12 [8,9] and YB 6 [10,11,12]. In this work, the band structure has been calculated using a full potential plane waves LMTO program [13] within a Local Density approach and Generalized Gradient Approximation [14].…”

Electronic Structure of Mixed Valent Systems

“…Thereafter, Travaglini and Wachter measured the reflectivity spectrum of SmB 6 in the energy range from 1 meV to 12 eV at 300 K and 4 K to investigate the energy-gap [81]. Kimura with coworkers measured the optical spectra of all single crystal rare-earth hexaborides RB 6 (R = La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Yb, and Y) in the energy region from 1 meV to 40 eV at 300 K and 13 K [76,[97][98][99]. Figure 18 shows, with a logarithmic scale, the calculated optical conductivity spectra of SmB 6 compared with experimental data measured at 13 K [76].…”