Title: [NCTS Seminar] Single-hole dynamics in 2D quantum magnets
Speaker: Prof. Anders W. Sandvik (Boston University)
Time: 2026/5/28 (Thu) 12:30-13:30
Place: NCTS Physics Lecture Hall, 4F, Chee-Chun Leung Cosmology Hall, NTU


Abstract
I will discuss quantum spin models on the square lattice, where certain multi-spin interactions can drive the Neel antiferromagnetic state of the conventional Heisenberg model into a spontaneously dimerized state. The quantum phase transition realizes the deconfined quantum-critical point (DQCP), with now well characterized scaling properties [1]. Here I will discuss the spectral properties of a single fermionic hole injected into the system, contrasting the behaviors when the host is in the Neel and dimerized phases and, in particular, at the DQCP [2]. Results are obtained using quantum Monte Carlo simulations, with a recently developed stochastic method for analytic continuation of imaginary-time Green's functions to real-frequency spectral functions [3]. Results at the DQCP support spin-charge separation and, therefore, the emergence of a ``holon metal'' [4]. 

[1] J. Takahashi, H. Shao, B. Zhao, W. Guo, and A. W Sandvik, arxiv:2405.06607.

[2] S. Yang and A. W. Sandvik, arXiv:2512.02962.

[3] H. Shao and A. W. Sandvik. Phys. Rep. 1003, 1 (2023).

[4] R. K. Kaul, A. Kolezhuk, M. Levin, S. Sachdev, and T. Senthil, Phys. Rev. B 75, 235122 (2007).