Unconventional magnetic oscillations in a kagome Mott insulator.

Zheng, Guoxin; Zhu, Yuan; Chen, Kuan-Wen; Kang, Byungmin; Zhang, Dechen; Jenkins, Kaila; Chan, Aaron; Zeng, Zhenyuan et al. · Proc Natl Acad Sci U S A · 2025

basic_science · Level V

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Abstract

In metals, electrons in a magnetic field undergo cyclotron motion, leading to oscillations in physical properties called quantum oscillations. This phenomenon has never been seen in a robust insulator because there are no mobile electrons. We report an exception to this rule. We study a Mott insulator on a kagome lattice which does not order magnetically down to milli-Kelvin temperatures despite antiferromagnetic interactions. We observe a plateau at magnetization equal to [Formula: see text] Bohr magneton per magnetic ion, accompanied by oscillations in the magnetic torque, reminiscent of quantum oscillations in metals. The temperature dependence obeys Fermi distribution. These phenomena are consistent with a quantum spin liquid state whose excitations are fermionic spinons with a Dirac-like spectrum coupled to an emergent gauge field.