[Seminar] Prof. Sandvik "The evolving story of deconfined quantum criticality"

Speaker

Prof. Anders W. Sandvik / Department of Physics, Boston University

Title

The evolving story of deconfined quantum criticality

Abstract

The hypothetical deconfined quantum-critical point (DQCP) was originally proposed as a generic transition point separating antiferromagnetic and singlet patterned phases (valence-bond solids) of 2D quantum magnets. Recent numerical studies instead point to a fine-tuned multi-critical DQCP with emergent SO(5) symmetry [1] that may also be connected to a gapless spin liquid phase [2]. I will discuss quantitative characterization of the multi-critical point from extensive quantum Monte Carlo simulations [1], showing, e.g., that scaling dimensions of various operators are in good agreement with bounds obtained with the conformal bootstrap method [3].

I will also discuss experiments on SrCu2(BO3)2 (the Shastry-Sutherland material) in a magnetic field under high pressure, which demonstrate a direct near-critical Low-temperature transition between an plaquette-singlet solid and an antiferromagnet, suggesting proximity to a DQCP [4]. In an ideal 2D Shastry-Sutherland system there may also be a spin liquid phase [2], though 3D effects and other perturbations likely destroy it in SrCu2(BO3)2.

[1] J. Takahashi, H. Shao, B. Zhao, W. Guo, A. W. Sandvik, arXiv:2405.06607.
[2] J. Yang, A. W. Sandvik, and L. Wang, PRB 105, L060409 (2022).
[3] S. M. Chester and N. Su, Phys. Rev. Lett. 132, 111601 (2024).
[4] Y. Cui et al., Science 380, 1179 (2023).

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