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arXiv · 2412.17194

Topological Semimetal KAlGe with Novel Electronic Instability

Toshiya Ikenobe·Takahiro Yamada·Jun-ichi Yamaura·Tamio Oguchi·Ryutaro Okuma·Daigorou Hirai·Hajime Sagayama·Yoshihiko Okamoto·Zenji Hiroi
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Abstract

Compounds with the anti-PbFCl structure exhibit a variety of electronic instabilities and intriguing physical properties. NaAlSi and NaAlGe are similar topological nodal-line semimetals, but they have distinct properties. NaAlSi is a superconductor at 6.8 K, whereas NaAlGe is an insulator with a pseudogap of approximately 100 K. Using the potassium-indium flux method, we succeeded in synthesizing a single crystal of KAlGe, a new anti-PbFCl compound. First principles electronic structure calculations reveal that KAlGe is isoelectronic with NaAlSi and NaAlGe. KAlGe undergoes a metal-to-metal transition at 89 K and exhibits no superconductivity above 1.8 K. The low temperature phase has significantly lower carrier density and extremely high mobility, similar to Dirac electron systems. Furthermore, X-ray diffraction experiments show a structural change that breaks the fourfold symmetry during the phase transition. Electron-phonon interactions may be responsible for superconductivity in NaAlSi, whereas excitonic electron-hole interactions are thought to play an important role in KAlGe and possibly NaAlGe. Our findings demonstrate that fascinating physics lies within the compound family.

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Toshiya Ikenobe, Takahiro Yamada, Jun-ichi Yamaura, Tamio Oguchi, Ryutaro Okuma, Daigorou Hirai, Hajime Sagayama, Yoshihiko Okamoto, Zenji Hiroi. 2024-12-22. Topological Semimetal KAlGe with Novel Electronic Instability. https://doi.org/10.1021/acs.chemmater.4c02284

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