学术预告|郭硕鸿讲座（第六十一期）（2024年3月29日16:40）：Kagome 超导体中的奇异物态

A general framework has been developed to solve the two-dimensional fully frustrated XY spin model on a Kagome lattice. The essential idea is to encode the ground-state local rules induced by frustrations in the local tensors of the partition function. Then the partition function is expressed in terms of a product of one-dimensional transfer matrix operator, whose eigen-equation can be solved by an algorithm of variational uniform matrix product states rigorously. The singularity of the entanglement entropy for the one-dimensional quantum analogue provides a stringent criterion to distinguish various phase transitions without identifying any order parameter a prior. Specially, we introduced a new representation to build the tensor network with local tensors lying on the centers of the elementary triangles of the Kagome lattice based on the duality transformation. Through a systematic numerical analysis of thermodynamic properties and correlation functions in the thermodynamic limit, we numerically proved that the model exhibits a single Berezinskii-Kosterlitz-Thouless phase transition, which is driven by the unbinding of 1/3 fractional vortex-antivortex pairs. Our result may be used to understand the charge-6e condensate observed experimentally in the vortex-antivortex lattice phase of the Kagome superconductors.

References

1. Tensor network approach to the fully frustrated XY model on a kagome lattice with a fractional vortex-antivortex pairing transition,Feng-Feng Song and Guang-Ming Zhang, Phys. Rev. B 108, 014424 (2023).

2. Evidence for multi-charge flux quantization in kagome superconductor ring devices,Jun Ge, Pinyuan Wang,Ying Xing, Qiangwei Yin, Anqi Wang, Jie Shen, Hechang Lei, Ziqiang Wang & Jian Wang, arXiv:2201.10352v2.