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arXiv · 2507.22362

Quantum Criticality by Interaction Frustration in a Square-Planar Lattice

Yi-Qiang Lin·Chang-Chao Liu·Jia-Xin Li·Bai-Jiang Lv·Kai-Xin Ye·Jia-Wen Zhang·Si-Qi Wu·Ya-Nan Zhang·Ye Chen·Jia-Yi Lu·Jing Li·Hua-Xun Li·Hao Li·Yi Liu·Cao Wang·Yun-Lei Sun·Hao Jiang·Hui-Qiu Yuan·Guang-Han Cao
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Abstract

We report experimental and theoretical investigations on ThCr$_2$Ge$_2$C, a metallic compound in which Cr$_2$C planes form a square-planar lattice. Neutron powder diffraction, magnetization, and specific heat measurements reveal no evidence of long-range magnetic order or short-range spin freezing down to 70~mK. Quantum critical behavior was indicated through logarithmic divergences in both the magnetic susceptibility and the specific heat divided by temperature. Resistivity measurements exhibit non-Fermi-liquid behavior, with a Fermi liquid recovered under magnetic fields or high pressures. First-principles calculations identify competing nearest-neighbor ($J_1$) and next-nearest-neighbor ($J_2$) exchange interactions, with $J_2/J_1 \sim -0.5$, pointing to strong magnetic frustration. The interaction frustration is reduced, and magnetically ordered phases are stabilized upon the application of negative or positive pressures. This work offers a rare example of zero-field, ambient pressure quantum criticality mainly driven by interaction frustration in a square lattice.

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Yi-Qiang Lin, Chang-Chao Liu, Jia-Xin Li, Bai-Jiang Lv, Kai-Xin Ye, Jia-Wen Zhang, Si-Qi Wu, Ya-Nan Zhang, Ye Chen, Jia-Yi Lu, Jing Li, Hua-Xun Li, Hao Li, Yi Liu, Cao Wang, Yun-Lei Sun, Hao Jiang, Hui-Qiu Yuan, Guang-Han Cao. 2025-07-30. Quantum Criticality by Interaction Frustration in a Square-Planar Lattice. https://arxiv.org/abs/2507.22362

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