Electronic structure of Mo_1−xRe_xalloys studied through resonant photoemission spectroscopy

Abstract

Abstract.We have studied the electronic structure of Mo rich Mo 1−x Re x alloys (0≤ x ≤0.4) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that with respect to the Fermi level E F , the d states lie mostly in the range 0 to -6 eV binding energy whereas s states lie in the range -4 to -10 eV binding energy. We have observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and other at about 45 eV photon energy. Our analysis suggest that the resonance at 35 eV photon energy is related to the Mo 4p-5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p-4d transition (threshold: 42 eV) and Re 5p-5d transition (threshold: 46 eV). In the CIS plot, the resonance at 35 eV incident photon energy for binding energy features in the range of E F (B.E. = 0) to -5 eV becomes progressively less prominent with the increasing Re concentration x and vanishes for x > 0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo 1−x Re x alloys, measured at 47 eV photon energy, reveal that the Re d like states appear near E F when Re is alloyed with Mo. These results indicate that interband s-d interaction, which is weak in Mo, increases with the increasing x and influences the nature of superconductivity in the alloys with higher x.

Localization of electronic states resulting from electronic topological transitions in the Mo$_{1-x}$Re$_x$ alloys: A photoemission study

“…Our studies revealed that the origin of the above observations is related to the phonon assisted interband s-d scattering between the band that newly appeared at the Fermi level (E f ) due to the ETT and the rest of the bands [8]. We have also shown from RPES studies on the alloys with x >> x C2 that the newly appeared band has Re5d like character [22]. Further analysis by Evans and Dowben revealed stronger Mo-Re orbital hybridization for x >> x C2 in comparison with the Mo-Mo or Re-Re bonding [36].…”

“…In this energy range, the photoemission spectra is more bulk sensitive [22]. Core levels were studied using X-ray photoemission spectroscopy (XPS) with Mg K α source (XR 50, SPECS).…”

“…Earlier, we have shown that the ETTs and the superconducting properties are coupled in the Mo 1−x Re x alloys [8,22]. Our previous studies [7,22] revealed that the appearance of Re 5d like states at the Fermi level above x > x C2 leads to multi-band superconductivity [23]. We have also shown that the scattering of s like electrons to Re 5d like states by the soft phonon modes is responsible for the enhancement of T C for x > x C2 [8].…”

“…The range of compositions where the sharp change in T C is observed is associated with two ETTs at the critical concentrations x C1 = 0.05 and x C2 = 0.11 [15][16][17][18][19][20][21]. Earlier, we have shown that the ETTs and the superconducting properties are coupled in the Mo 1−x Re x alloys [8,22]. Our previous studies [7,22] revealed that the appearance of Re 5d like states at the Fermi level above x > x C2 leads to multi-band superconductivity [23].…”

Comment on ‘Electronic structure of Mo(1−x)Rexalloys studied through resonant photoemission spectroscopy’

“…The resonant photoemission intensities, found within 'Electronic structure of Mo 1−x Re x alloys studied through resonant photoemission spectroscopy', have implications beyond those discussed, by Sundar et al [1]. The suppression of the resonant photoemission intensities, as a functional of Mo 1−x Re x alloy composition [1], parallel similar trends to those found for Gd 1−x Ni x alloy films [2], and imply strong hybridization, considerable short-range in the Mo 1−x Re x alloy system.…”