New Principle for “One-Way Current Flow” in Kagome Metals

In the kagome metal CsV₃Sb₅, a newly discovered superconductor with strong geometric frustration, a variety of exotic quantum phases emerge, including loop-current states where time-reversal symmetry is broken and nanoscale persistent currents circulate. Recently a rectification effect has been observed in this material, where electrical current preferentially flows in one direction. In CsV₃Sb₅ the polarity of rectification can be reversed by applying a very small switching magnetic field, raising the possibility that this represents a novel rectification effect originating from quantum phases such as the loop-current state. Until now, however, the theoretical foundation of this phenomenon has remained elusive.

In this study, the researchers discovered a new principle that explains the rectification effect observed in kagome metals. They demonstrated that the chirality of loop currents can be switched by an external magnetic field, thereby reversing the polarity of the rectification effect. Furthermore, they found that rectification is strongly enhanced by a quantum geometric effect arising from the modification of the electron wavefunction by loop currents. These findings not only shed new light on the elusive loop-current phase in kagome metals but also open exciting prospects for novel device applications that harness quantum rectification.

Papers

Journal: Proceedings of the National Academy of Sciences of the United States of America

Title: Quantum-metric-induced giant and reversible nonreciprocal transport phenomena in chiral loop-current phases of kagome metals

Authors: Rina Tazai, Youichi Yamakawa, Takahiro Morimoto, Hiroshi Kontani

DOI: 10.1073/pnas.2503645122