Local spectroscopy of loop current order with individual magnetic atoms

Jiangchang Zheng; Caiyun Chen; Xu Zhang; Daniel J. Schultz; Gaopei Pan; Chen Chen; Yuan Da Liao; Ganesh Pokharel; Andrea Capa Salinas; Qirong Yao; Luanjing Li; Yizhou Wei; Hoi Chun Po; Ding Pan; Han-Qing Wu; Stephen D. Wilson; Jörg Schmalian; Zi Yang Meng; Berthold Jäck

arXiv · 2503.19032

Local spectroscopy of loop current order with individual magnetic atoms

Jiangchang Zheng·Caiyun Chen·Xu Zhang·Daniel J. Schultz·Gaopei Pan·Chen Chen·Yuan Da Liao·Ganesh Pokharel·Andrea Capa Salinas·Qirong Yao·Luanjing Li·Yizhou Wei·Hoi Chun Po·Ding Pan·Han-Qing Wu·Stephen D. Wilson·Jörg Schmalian·Zi Yang Meng·Berthold Jäck

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Abstract

Hidden ordered states--characterized by order parameters that elude conventional probes--pose a fundamental challenge for their identification in quantum materials. Recent experiments report evidence for time-reversal symmetry breaking orbital magnetic order and anomalous transport signatures in the $2a\times2a$ charge density wave state of the kagome metal CsV$_3$Sb$_5$ at a temperature $T<30\,$K. Theoretical analyses propose that a time-reversal symmetry breaking loop-current order could exist as the ground state of this charge density wave. However, this microscopic interpretation remains debated and experimentally unverified. In this work, we employ individual magnetic atoms as local quantum sensors to examine the quasiparticle excitations of the charge density wave in CsV$_3$Sb$_5$ with the scanning tunneling microscope. Our spectroscopic measurements show that the magnetic moment of Co induces a spatially localized $dI/dV$ peak inside the spectral gap of the charge density wave near the Fermi energy. Conducting temperature-dependent spectroscopy, we find that this spectral feature emerges at $T<30\,$K. By comparing our experimental observations with results of quantum many-body simulations and realistic tight-binding model calculations, we show that this spectroscopic signature can be naturally interpreted as a local flux defect in a loop current ordered state, arising from the Kondo coupling of the magnetic moment of Co with the loop current electrons. The excellent agreement between our experimental and theoretical results suggests the presence of loop-current order in the $2a\times2a$ charge density wave of CsV$_3$Sb$_5$ at $T<30\,$K. Our results provide a microscopic picture to the observation of time-reversal symmetry breaking orbital magnetism and anomalous transport signatures detected in measurements of the macroscopic material properties.

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Jiangchang Zheng, Caiyun Chen, Xu Zhang, Daniel J. Schultz, Gaopei Pan, Chen Chen, Yuan Da Liao, Ganesh Pokharel, Andrea Capa Salinas, Qirong Yao, Luanjing Li, Yizhou Wei, Hoi Chun Po, Ding Pan, Han-Qing Wu, Stephen D. Wilson, Jörg Schmalian, Zi Yang Meng, Berthold Jäck. 2025-03-24. Local spectroscopy of loop current order with individual magnetic atoms. https://arxiv.org/abs/2503.19032

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