Optical conductivity and vibrational spectra of the narrow-gap semiconductor FeGa${}_3$

Abstract

Intermetallic narrow-gap semiconductors have been intensively explored due to their large thermoelectric power at low temperatures and a possible role of strong electronic correlations in their unusual thermodynamic and transport properties. Here we study the optical spectra and vibrational properties of $\mathrm{FeG}{\mathrm{a}}_3$ single crystal. The optical conductivity indicates that $\mathrm{FeG}{\mathrm{a}}_3$ has a direct band gap of $\sim 0.7$\,eV, consistent with density functional theory (DFT) calculations. Most importantly, we find a substantial spectral weight also below 0.4~eV, which is the energy of the indirect (charge) gap found in resistivity measurements and ab initio calculations. We find that the spectral weight below the gap decreases with increasing temperature, which indicates that it originates from the impurity states and not from the electronic correlations. Interestingly, we did not find any signatures of the impurity states in vibrational spectra. The infrared and Raman vibrational lines are narrow and weakly temperature dependent. The vibrational frequencies are in excellent agreement with our DFT calculations, implying a modest role of electronic correlations. Narrow M\" ossbauer spectral lines also indicate high crystallinity of the sample.

References in corpus (21)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Phonons and related properties of extended systems from density-functional perturbation theory
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Ab initio calculation of excitonic effects in the optical spectra of semiconductors
• Anisotropy and large magnetoresistance in narrow gap semiconductor FeSb2
• Use of X-ray scattering functions in Kramers-Kronig analysis of reflectance
• Signatures of electronic correlations in iron silicide
• Thermopower of correlated semiconductors : application to FeAs2 and FeSb2
• Infrared spectroscopic study of phonons coupled to charge excitations in FeSi
• Thermoelectricity in correlated narrow-gap semiconductors
• Huge Thermoelectric Power Factor: FeSb2 versus FeAs2 and RuSb2
• Optical investigation of the metal-insulator transition in $FeS{b}_2$
• Phonon-drag effect in FeGa3
• Unified picture for the colossal thermopower compound FeSb${}_2$
• Electronic correlations in FeGa${}_3$ and the effect of hole doping on its magnetic properties
• Strong electron correlations in FeSb2: An optical investigation and comparison with RuSb2
• Evidence for electron-phonon interaction in Fe${}_{1-x}$M${}_x$Sb${}_2$ (M=Co, Cr) single crystals
• Vacancy defect control of colossal thermopower in FeSb2
• Unusual electronic and vibrational properties in the colossal thermopower material FeSb${}_2$
• Lattice dynamics of FeSb2
• Structural and electronic properties of Fe(AlxGa1-x)3 system