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arXiv · 2203.07607

Magnetically hidden state on the ground floor of the magnetic Devil's staircase

Shusaku Imajo·Naofumi Matsuyama·Toshihiro Nomura·Takumi Kihara·Shintao Nakamura·Christophe Marcenat·Thierry Klein·Gabriel Seyfarth·Chengchao Zhong·Hiroshi Kageyama·Koichi Kindo·Tsutomu Momoi·Yoshimitsu Kohama
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Abstract

We investigated the low-temperature and high-field thermodynamic and ultrasonic properties of SrCu2(BO3)2, which exhibits various plateaux in its magnetization curve above 27~T, called a magnetic Devil's staircase. The results of the present study confirm that magnetic crystallization, the first step of the staircase, occurs above 27~T as a 1st-order transition accompanied by a sharp singularity in heat capacity $C_p$ and a kink in the elastic constant. In addition, we observe a thermodynamic anomaly at lower fields around 26~T, which has not been previously detected by any magnetic probes. At low temperatures, this magnetically hidden state has a large entropy and does not exhibit Schottky-type gapped behavior, which suggests the existence of low-energy collective excitations. Based on our observations and theoretical predictions, we propose that magnetic quadrupoles form a spin-nematic state around 26~T as a hidden state on the ground floor of the magnetic Devil's staircase.

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Shusaku Imajo, Naofumi Matsuyama, Toshihiro Nomura, Takumi Kihara, Shintao Nakamura, Christophe Marcenat, Thierry Klein, Gabriel Seyfarth, Chengchao Zhong, Hiroshi Kageyama, Koichi Kindo, Tsutomu Momoi, Yoshimitsu Kohama. 2022-03-15. Magnetically hidden state on the ground floor of the magnetic Devil's staircase. https://doi.org/10.1103/physrevlett.129.147201

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