Nonequilibrium properties of correlated quantum matter are being intensively investigated because of the rich interplay between external driving and the many-body correlations. Of particular interest is the nonequilibrium behavior near a quantum critical point (QCP), where the system is delicately balanced between different ground states. We present both an analytical calculation of the nonequilibrium steady-state current in a critical system and experimental results to which the theory is compared. The system is a quantum dot coupled to resistive leads: a spinless resonant level interacting with an Ohmic dissipative environment. A two-channel Kondo-like QCP occurs when the level is on resonance and symmetrically coupled to the leads, conditions achieved by fine tuning using electrostatic gates. We calculate and measure the nonlinear current as a function of bias ($I\text{−}V$ curve) at the critical values of the gate voltages corresponding to the QCP. The quantitative agreement between the experimental data and the theory, with no fitting parameter, is excellent. As our system is fully accessible to both theory and experiment, it provides an ideal setting for addressing nonequilibrium phenomena in correlated quantum matter.

中文翻译：

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非平衡量子临界稳态：通过耗散共振能级的传输

由于外部驱动和多体相关之间的丰富相互作用，正在深入研究相关量子物质的非平衡性质。特别令人感兴趣的是量子临界点（QCP）附近的非平衡行为，在该量子点，系统在不同基态之间精确地平衡。我们同时介绍了关键系统中非平衡稳态电流的解析计算和与理论进行比较的实验结果。该系统是耦合到电阻引线的量子点：与欧姆耗散环境相互作用的无旋转共振能级。当电平处于谐振状态并且对称耦合到引线时，会出现两通道的类似Kondo的QCP，这是通过使用静电门进行微调来实现的。$\mathrm{一世}\text{-}V$曲线）对应于QCP的栅极电压的临界值。在没有拟合参数的情况下，实验数据与理论之间的定量一致性非常好。由于我们的系统理论和实验均可完全使用，因此它为解决相关量子物质中的非平衡现象提供了理想的设置。