Shingo Kisanuki | Searcharxiv

arXiv2026

Chiral phonons in sixfold chiral CrSi$_2$: Raman spectroscopy and first-principles calculations

Chiral phonons have been identified in several chiral crystals, primarily in those with trigonal symmetry and threefold screw axes. In this study, chiral phonons in CrSi$_2$, a chiral crystal with a sixfold helical structure, were investigated. Circularly polarized Raman spectroscopy revealed a subtle splitting of doubly degenerate $E_2$ phonon modes between cross-circular polarization configurations. These observations, supported by first-principles phonon calculations, indicate the presence of chiral phonons in CrSi$_2$, expanding the scope of materials that exhibit chiral vibrational modes beyond the conventional trigonal class.

cond-mat.mtrl-sci↗

arXiv2024

Superconductivity in Ternary Germanite TaAl$_{x}$Ge$_{2-x}$ with a C40 chiral structure

We report a new family of chiral intermetallic superconductors TaAl$_{x}$Ge$_{2-x}$. The mother compound TaGe$_2$ has a C40-type chiral hexagonal crystal structure with a pair of enantiomorphic space groups of $P6{_2}22$ and $P6{_4}22$. By substituting Ge with Al, TaAl$_{x}$Ge$_{2-x}$ polycrystals with the C40 structure were synthesized with Al substitution $x$ from 0 to 0.8. Magnetic susceptibility, magnetization curves and electrical resistivity revealed that TaAl$_{x}$Ge$_{2-x}$ with $x$ of 0.2 to 0.4 was a type-II superconductor with a superconducting transition temperature $T_{\rm c}$ of 2.0 to 2.2 K. The superconductivity disappeared or was largely suppressed at $x$ less than 0.2 and more than 0.4, although all the measurements were performed at temperatures above 1.8 K. An emergence of superconductivity is discussed in terms of the lattice constants changes with the Al substitution.

cond-mat.supr-con↗