Exotic density-wave (DW) orders in strongly correlated metals have been discovered one after another and found to be universal now. The multistage unconventional DW (with non-A1g symmetry) orders in frustrated kagome metal AV3Sb5 (A=Cs,Rb,K) and its interplay with exotic superconductivity attract increasing attention. We find that the star-of-David bond-order originates from the inter-sublattice electron correlation due to the paramagnon interference mechanism. In addition, we uncover that moderate bond-order fluctuations mediate s-wave and triplet p-wave superconductivity. The obtained impurity-induced change in the SC state is consistent with recent electron-irradiation measurements. Furthermore, we discovered that the time-reversal symmetry-breaking loop current order is naturally caused by the bond-order fluctuations. 

More interestingly, the coexistence of the charge-current order and the bond-order gives rise to novel quantum states, and the coexisting state is very sensitive to the outer magnetic field and the uniaxial strain field. To understand the multiple quantum phase transitions in kagome metals, we construct the Ginzburg-Landau (GL) free-energy theory under the outer fields and explain why the loop-current order is drastically stabilized under the magnetic and strain fields [4]. We also discuss the characteristic nonreciprocal transport phenomena in the coexisting quantum phase, such as the giant electronic magnetochiral anisotropy (eMChA) reported by Guo et al, Nature 611, 461 (2022). 

Biography

Dr. Kontani obtained his PhD from Kyoto University in Japan in 1996. He then worked as an Assistant Professor at ISSP, University of Tokyo, and later became an Associate Professor at Saitama University. In 2004, he joined Nagoya University. Prof. Kontani is a distinguished expert in unconventional superconductivity, strongly correlated systems, and quantum phase transitions. His significant contributions to transport and superconductivity in strongly correlated systems were honored with Ryogo Kubo Memorial Prize in 2013.

Inviter

Xian-Xin Wu