Structural responses incipient to pressure-driven antiferromagnetic quantum critical point of van der Waals heavy-fermion metal CeSiI

Hanming Ma; Tong Shi; Wenhao Li; Qingxin Dong; Xiaoli Ma; Shaoheng Ruan; Zhongjin Wu; Pengtao Yang; Zhaoming Tian; Jianping Sun; Yoshiya Uwatoko; Xiaohui Yu; Hechang Lei; Bosen Wang; Jinguang Cheng

arXiv · 2606.12222

Structural responses incipient to pressure-driven antiferromagnetic quantum critical point of van der Waals heavy-fermion metal CeSiI

Hanming Ma·Tong Shi·Wenhao Li·Qingxin Dong·Xiaoli Ma·Shaoheng Ruan·Zhongjin Wu·Pengtao Yang·Zhaoming Tian·Jianping Sun·Yoshiya Uwatoko·Xiaohui Yu·Hechang Lei·Bosen Wang·Jinguang Cheng

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Abstract

CeSiI is a van der Waals heavy-fermion metal recently found to exhibit unconventional superconductivity near a pressure-induced antiferromagnetic quantum critical point (QCP) at Pc =6 GPa. Here, we report a comprehensive single-crystal X-ray diffraction study of CeSiI under high pressures up to 8.3 GPa at room temperature, revealing subtle structural responses that precede pressure-driven QCP. We find that the unit-cell volume decreases smoothly upon compression without showing any structural phase transition in the investigated pressure range. Intriguingly, we observe abrupt and concurrent anisotropic responses of the lattice parameters around Pc =6 GPa, i.e., the a-axis contracts while the c-axis enlongated suddenly, with the unit-cell volume smoothily varies with pressure. Structural refinements further show that these lattice anomalies primarily originate from changes of Ce-Ce and Ce-Si bond lengths, as well as a flattening of the inner honeycomb Si layer within the CeSiI monolayer around Pc. Our findings establish an interesting case linking pressure-driven electronic transition of QCP at low temperatures to incipient structural responses at room temperature, thereby providing fresh insight into the pressure-temperature phase diagram of CeSiI.

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Hanming Ma, Tong Shi, Wenhao Li, Qingxin Dong, Xiaoli Ma, Shaoheng Ruan, Zhongjin Wu, Pengtao Yang, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Xiaohui Yu, Hechang Lei, Bosen Wang, Jinguang Cheng. 2026-06-10. Structural responses incipient to pressure-driven antiferromagnetic quantum critical point of van der Waals heavy-fermion metal CeSiI. https://arxiv.org/abs/2606.12222

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