从有效温度到驱动-耗散量子临界中的非玻尔兹曼态选择

中文摘要 AI 辅助

非平衡量子临界稳态能否用有效温度描述仍是一个悬而未决的问题。我们在一个电压偏置的电子Lipkin--Meshkov--Glick模型中探讨了这一问题，该模型是一个将集体自旋耦合到金属引线的最小驱动-耗散模型。受控的大$N$处理揭示了一个与闭合模型不同的过阻尼开放量子临界区域。围绕由温度和电压组织的量子临界扇区被探索，发现涨落由有效温度$T_{\ m eff}$支配。在强偏置下，转变通过一个三临界点变为一级相变。值得注意的是，相同的$T_{\ m eff}$也支配强驱动区域，但此时它随整个序参量景观而变化。因此，稳态由非玻尔兹曼规则选择，将一级相变从确定性势的等深点移开。因此，驱动临界性仍由有效温度组织，同时揭示了非热态选择。

英文摘要

Whether a nonequilibrium quantum-critical steady state can be described by an effective temperature remains an open question. We address it in a voltage-biased electronic Lipkin--Meshkov--Glick model, a minimal driven-dissipative model of a collective spin coupled to metallic leads. A controlled large-$N$ treatment reveals an overdamped open quantum-critical regime distinct from the closed model. The surrounding quantum critical fan, organized by temperature and voltage, is explored and fluctuations are found to be governed by an effective temperature $T_{\rm eff}$. At strong bias, the transition becomes first-order through a tricritical point. Remarkably, the same $T_{\rm eff}$ governs the strongly driven regime, but now varies across the entire order-parameter landscape. The steady state is therefore selected by a non-Boltzmann rule, shifting the first-order transition away from the equal-depth point of a deterministic potential. Driven criticality thus remains organized by an effective temperature while revealing non-thermal state selection.

发表机构

• Instituto Superior Técnico, Universidade de Lisboa（里斯本理工大学）
• Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）

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