Single-hole Dynamics in 2D Quantum Magnets

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Abstract

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I will discuss S=1/2 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 states. 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 dimerizes 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. I will discuss this analytic continuation method as an example of an interesting inverse problem and then present results for the spectral functions and their interpretation, in particular spin-charge separation and the emergence of a “holon metal” [3] from the DQCP.

 

[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] R. K. Kaul, A. Kolezhuk1, M. Levin, S. Sachdev, and T. Senthil, Phys. Rev. B 75, 235122 (2007).

 

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About the Speaker

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Anders Sandvik is a Professor of Physics at Boston University. He completed his PhD at the University of California, Santa Barbara, in 1993, then carried out postdoctoral work at Florida State University and the University of Illinois at Urbana-Champaign before returning to his native country as a Senior Fellow of the Academy of Finland in 2000. He joined the faculty of Boston University in 2004. He is a Fellow of the American Physical Society, a Simons Investigator in Physics, and the 2021 recipient of the Aneesur Rahman Prize for Computational Physics. He received a Guggenheim Fellowship in 2025. His research focuses on computational studies in quantum many-body physics. He is the inventor of the Stochastic Series Expansion method and several other widely used simulation techniques. His studies of quantum lattice models have provided unique insights into collective quantum many-body states and their quantum phase transitions.