2026-09-22 バッファロー大学（UB）
An interpretation of quantum fluctuations, depicted as a dynamic, ever-changing 3D terrain. A University at Buffalo-led study found that such fluctuations play a role in the transition from an ultraslow spin glass to the ultrafast, highly entangled behavior related to black hole physics.
＜関連情報＞
- https://www.buffalo.edu/news/releases/2026/09/ultraslow-quantum-magnetism-to-ultrafast-black-hole-physics.html
- https://journals.aps.org/prl/abstract/10.1103/81qf-zd3y
無限範囲量子ハイゼンベルクスピングラスにおけるサチデフ・イェ・キタエフ臨界へのクロスオーバー Crossover to Sachdev-Ye-Kitaev Criticality in an Infinite-Range Quantum Heisenberg Spin Glass
Hossein Hosseinabadi, Subir Sachdev, and Jamir Marino
Physical Review Letters Published: 17 September, 2026
DOI: https://doi.org/10.1103/81qf-zd3y
Abstract
A central question in frustrated quantum magnets is how quantum fluctuations destabilize spin-glass order and promote quantum spin-liquid behavior. We study the equilibrium dynamics of an infinite-range quantum Heisenberg model with random couplings, in which local magnetic moments arise from Nf flavors of spinful fermions. We employ an expansion in Nf, which controls the strength of quantum fluctuations, and self-consistently include 1/Nf corrections to the Luttinger-Ward functional. In the large-Nf limit, where quantum fluctuations are weak, the high- and low-temperature phases are respectively paramagnetic and spin glass ordered, with a transition temperature independent of Nf. For small numbers of fermionic flavors, however, quantum fluctuations substantially suppress the ordering temperature. We show that this behavior reflects the proximity of the system to a Sachdev-Ye-Kitaev (SYK) regime, realizing quantum spin-liquid dynamics over a broad range of finite frequencies, where both fermionic and spin spectral densities display critical behavior over a broad range of finite frequencies, with the latter exhibiting the scale-invariant form x′′(ω) ∼sgn(ω). At the lowest energies and temperatures, spin glass dynamics ultimately take over, producing a universal sub-Ohmic dynamical spin susceptibility x′′(ω) ∼sgn(ω)√|ω|. Our results highlight a direct connection between the suppression of spin-glass order and the emergence of SYK criticality in a frustrated quantum magnet.
