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arXiv · 2606.25251

NMR evidence for a loop-current state with broken $C_6$ symmetry in the charge-ordered CsV$_3$Sb$_5$

X. Y. Feng·Z. Zhao·J. Dou·S. Li·J. Luo·J. Yang·H. T. Yang·H. -J. Gao·R. Zhou·Guo-qing Zheng
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Abstract

Loop-current (LC) order and the associated time-reversal symmetry breaking (TRSB) are pivotal for understanding hidden magnetism and unconventional superconductivity in strongly correlated quantum materials. The recently discovered kagome metal CsV$_3$Sb$_5$ provides a unique platform for exploring these intertwined phenomena. In this study, we utilize $^{121}$Sb nuclear quadrupole resonance (NQR) and $^{51}$V nuclear magnetic resonance (NMR) measurements to investigate the possible existence of the LC order in CsV$_3$Sb$_5$. Below $T^\ast \approx 45$ K, we observe a field-independent NMR linewidth broadening at the V site in a high-quality single crystal, which indicates an internal magnetic field of 3.6 Oe at the V position. We show that this internal field arises from a static LC state that produces orbital magnetic moments $\mu_{\rm orb}$ ranging from 0.002 to 0.01 $\mu_B$. Detailed analysis suggests that the observed LC state breaks $C_6$ rotational symmetry to possess a low symmetry of $C_2$. Our results provide microscopic evidence for LC order in the charge density wave (CDW) phase of CsV$_3$Sb$_5$ and show that TRSB is intertwined with electronic nematicity, imposing stringent constraints on microscopic descriptions of the kagome CDW and its relation to superconductivity.

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X. Y. Feng, Z. Zhao, J. Dou, S. Li, J. Luo, J. Yang, H. T. Yang, H. -J. Gao, R. Zhou, Guo-qing Zheng. 2026-06-24. NMR evidence for a loop-current state with broken $C_6$ symmetry in the charge-ordered CsV$_3$Sb$_5$. https://arxiv.org/abs/2606.25251

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