Time-reversal-like degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound

Abstract

In magnetic crystals, despite the explicit breaking of time-reversal symmetry, two equilibrium states related by time reversal are always energetically degenerate. In ferromagnets such time-reversal degeneracy can be manifested by hysteresis loops in the magnetic field dependence of the magnetization and, if metallic, in the anomalous Hall effect. Importantly, both quantities simply change signs but not their absolute sizes under time reversal, which follows from their fundamental definitions. Our integral experimental and theoretical study shows that in the metallic kagome spin ice HoAgGe subject to finite magnetic fields parallel to the kagome plane, an emergent time-reversal-like degeneracy appears between magnetic states that have the same energy and net magnetization, but different sizes of the anomalous Hall effect. These degeneracies are unraveled by finite hysteresis in the field-dependent anomalous Hall effect contrasted with the vanishing hysteresis in the magnetization, which appears only at low-temperatures T$<$4K when the kagome spin ice is fully ordered into $\sqrt{3}$$\times$$\sqrt{3}$ state. By explicitly determining the degenerate states and calculating the corresponding physical properties using a tight-binding model, we nailed down the time-reversal-like operation that transforms these degenerate states into each other. The operation is related to the nontrivial distortion of the kagome lattice in HoAgGe and is effective only because of the richness of degenerate states unique to kagome spin ice. Our work points to the powerful role of the anomalous Hall effect to diagnose hidden symmetries in frustrated spin systems.

This is the initial submission version during first part of 2022, and the recent version after several round significant modifications will appear on Nature Physics later

References in corpus (13)

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Cited by in corpus (8)

• Tunable topological transitions in the frustrated magnet HoAgGe
• Local excitation of kagome spin ice magnetism in HoAgGe seen by scanning tunneling microscopy
• Antiferromagnetic ordering and critical behavior induced giant magnetocaloric effect in distorted kagome lattice Gd${}_3$BWO${}_9$
• Lattice dynamics and spin-phonon coupling in the kagome spin ice HoAgGe
• Interplay of short-range bond order and A-type antiferromagnetic order in metallic triangular lattice GdZn${}_3$P${}_3$
• Noncollinear antiferromagnetic structure and physical properties of CrRhAs with distorted kagome lattice
• Hall mass and transverse Noether spin currents in noncollinear antiferromagnets
• Magnetic and electric properties of the metallic kagome antiferromagnet CrRhAs