Optical study of the electronic structure of locally noncentrosymmetric <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Ce</mml:mi><mml:msub><mml:mi>Rh</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Shin‐ichi Kimura, J. Sichelschmidt, Seunghyun Khim
Abstract
The electronic structures of the heavy-fermion superconductor $\mathrm{Ce}{\mathrm{Rh}}_{2}{\mathrm{As}}_{2}$ with local inversion symmetry breaking and the reference material $\mathrm{La}{\mathrm{Rh}}_{2}{\mathrm{As}}_{2}$ have been investigated by using experimental optical conductivity $[{\ensuremath{\sigma}}_{1}(\ensuremath{\omega})]$ spectra and first-principles density functional theory calculations. The low-temperature ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})$ spectra of $\mathrm{La}{\mathrm{Rh}}_{2}{\mathrm{As}}_{2}$ revealed a broad peak at $\ensuremath{\sim}0.1\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ and a sharp peak at $\ensuremath{\sim}0.5\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ after a subtraction of the Drude contribution of free carriers. The peak features and the background intensity were nicely reproduced in calculated ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})$ spectra from DFT calculations, implying a conventional metallic nature. In $\mathrm{Ce}{\mathrm{Rh}}_{2}{\mathrm{As}}_{2}$, two mid-IR peaks at $\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\sim}0.12$ and 0.4 eV corresponding to the unoccupied Ce $4{f}_{5/2}$ and $4{f}_{7/2}$ states, respectively, were strongly developed with decreasing temperature, which suggests the emergence of hybridization states between the conduction and $4f$ electrons. We compared the temperature dependence of the mid-IR peaks of $\mathrm{Ce}{\mathrm{Rh}}_{2}{\mathrm{As}}_{2}$ with corresponding data from $\mathrm{Ce}{\mathrm{Cu}}_{2}{\mathrm{Si}}_{2}$ and $\mathrm{Ce}{\mathrm{Ni}}_{2}{\mathrm{Ge}}_{2}$ in a $\mathrm{Th}{\mathrm{Cr}}_{2}{\mathrm{Si}}_{2}$-type structure to examine the possible impact of local inversion symmetry breaking on electronic structures.