弱耦合环境下的过阻尼
Overdamping by weakly coupled environments
摘要：
一个与快速环境弱相互作用的量子系统通常会经历复频率的弛豫，其虚部是与环境耦合的阻尼率的平方，符合费米的“黄金法则”。我们证明了各种模型（自旋阻尼谐振子或随机矩阵浴，量子扩散，量子布朗运动），增加耦合到一个临界值仍然足够小，允许弱耦合马尔可夫主方程，一个新的松弛制度可以发生。在这种情况下，复频率失去了它们的实部，使得过程变得过阻尼。我们的研究结果提出了质疑的标准信念，过度阻尼是唯一的强耦合功能。
英文摘要：
A quantum system weakly interacting with a fast environment usually undergoes a relaxation with complex frequencies whose imaginary parts are damping rates quadratic in the coupling to the environment, in accord with Fermi's ``Golden Rule''. We show for various models (spin damped by harmonic-oscillator or random-matrix baths, quantum diffusion, quantum Brownian motion) that upon increasing the coupling up to a critical value still small enough to allow for weak-coupling Markovian master equations, a new relaxation regime can occur. In that regime, complex frequencies lose their real parts such that the process becomes overdamped. Our results call into question the standard belief that overdamping is exclusively a strong coupling feature.
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