Ultrasonic observation of small Fermi surfaces in La$T$In$_5$ ($T$ = Co, Rh, Ir)

Ryosuke Kurihara; Yusuke Hirose; Kazuki Matsui; Atsushi Miyake; Ryoma Tsunoda; Masaki Kondo; Rikio Settai; Mitsuhiro Akatsu; Yuichi Nemoto; Hiroshi Yaguchi; Masashi Tokunaga

arXiv · 2512.06235

Ultrasonic observation of small Fermi surfaces in La$T$In$_5$ ($T$ = Co, Rh, Ir)

Ryosuke Kurihara·Yusuke Hirose·Kazuki Matsui·Atsushi Miyake·Ryoma Tsunoda·Masaki Kondo·Rikio Settai·Mitsuhiro Akatsu·Yuichi Nemoto·Hiroshi Yaguchi·Masashi Tokunaga

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Abstract

We performed high-field ultrasonic measurements on La$T$In$_5$ ($T$ = Co, Rh, Ir) to reveal the origin of the small Fermi surface that was recently observed in LaRhIn$_5$ with an oscillation frequency of 6.8 T. We observed quantum oscillations originating from this Fermi surface in LaRhIn$_5$. In addition, we revealed that LaCoIn$_5$ and LaIrIn$_5$ exhibit quantum osciilations with frequencies below 100 T, indicating hidden Fermi surfaces in these compounds. Furthermore, Co-substituted LaRhIn$_5$ exhibited quantum oscillations with a frequency of 10 T. Our results suggest that the small Fermi surface originates from bulk properties and that $3d$ electrons of the transition metal contribute to its formation.

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Ryosuke Kurihara, Yusuke Hirose, Kazuki Matsui, Atsushi Miyake, Ryoma Tsunoda, Masaki Kondo, Rikio Settai, Mitsuhiro Akatsu, Yuichi Nemoto, Hiroshi Yaguchi, Masashi Tokunaga. 2025-12-06. Ultrasonic observation of small Fermi surfaces in La$T$In$_5$ ($T$ = Co, Rh, Ir). https://arxiv.org/abs/2512.06235

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