Q-dependent electronic excitations in osmium: Pressure- and temperature-induced effects

Abstract

Raman scattering by electrons and phonons has been studied in single crystals of the 5d transition-metal osmium under pressures up to 60 GPa in the temperature range of 10-300 K. An anomalous increase in the electronic light-scattering cross section was found in the pressure range of 20-30 GPa with the use of green and blue excitation wavelengths. At these conditions, we observe an appearance of well-defined electronic peaks at ϳ580 cm −1 for the wave-vector direction q ʈ ͓0001͔ and at ϳ350 cm −1 for q ʈ ͓1010͔. The comparison of q dependencies measured and calculated from the first-principles spectra suggests a strong volume-and temperature-dependent renormalization of the energies and damping of the electronic states near the Fermi level.

Raman Spectroscopy at High Pressures

“…The first-principle band-structure calculations suggest changes in the FS topology that occur due to the E 2g phonon displacements (Figure 7). Thus, one can speculate that these phenomena are responsible for the anomalies observed by Raman spectroscopy [113] and in the lattice parameters [114] above 20 GPa.…”

“…The application of pressure may modify both the electronic band structure near the Fermi level and internal scattering processes, which would affect the Raman spectra. An anomalous increase in the electronic lightscattering cross-section was found in Os the pressure range of 20-30 GPa with green and blue excitation wavelengths [113]. At these conditions, an appearance of well-defined electronic peaks at 580 cm −1 for the wave-vector direction q [0001] and at 350 cm −1 for q [1010] has been observed.…”

“…The red solid and green dashed lines are the band structures calculated for distorted structures obtained by the opposite atomic displacements corresponding to the X-polarized component of the degenerate E 2g modes. Fermi level is at zero energy[113].…”

High-pressure Raman study of osmium and rhenium up to 200 GPa and pressure dependent elastic shear modulus C 44

“…To prevent specular reflection from being directed to the spectrometer and reduce the signal from the diamond, a lateral excitation technology (typical 35 • incidence angle for the exciting radiation) was used in high-pressure Raman experiments on HCP metals, such as Be, [21] Fe, [22] Re [23] and Os. [24,25] The Raman scattering on the metals, however, are limited by the detection based on conventional experimental set-up. Up to now, high-pressure Raman scattering on the HCP Os and Re is only extended to 60 GPa [25] and 138 GPa, [26] respectively.…”

“…[24,25] The Raman scattering on the metals, however, are limited by the detection based on conventional experimental set-up. Up to now, high-pressure Raman scattering on the HCP Os and Re is only extended to 60 GPa [25] and 138 GPa, [26] respectively. There are far narrow pressure ranges that need to be investigated, and this implies that the influence of pressure upon HCP metals' elastic properties has not yet been unambiguously determined.…”