The understanding of the dynamics of nonequilibrium cooling and heating processes at the nanoscale is still an open problem. These processes can follow surprising relaxation paths due to, e.g., memory effects, which significantly alter the expected equilibration routes. The Kovacs effect can take place when a thermalization process is suddenly interrupted by a change of the bath temperature, leading to a nonmonotonic evolution of the energy of the system. Here, we demonstrate that the Kovacs effect can be observed in the thermalization of the center of mass motion of a levitated nanoparticle. The temperature is controlled during the experiment through an external source of white Gaussian noise that mimics an effective thermal bath at a temperature that can be changed faster than any relaxation time of the system. We describe our experiments in terms of the dynamics of a Brownian particle in a harmonic trap without any fitting parameter, suggesting that the Kovacs effect can appear in a large variety of systems.

中文翻译：

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光悬浮纳米粒子的 Kovacs 记忆效应

对纳米级非平衡冷却和加热过程动力学的理解仍然是一个悬而未决的问题。由于例如记忆效应，这些过程可以遵循令人惊讶的松弛路径，这显着改变了预期的平衡路径。当热化过程被浴温的变化突然中断时，会发生科瓦奇效应，导致系统能量的非单调演变。在这里，我们证明了可以在悬浮纳米颗粒的质心运动的热化中观察到 Kovacs 效应。在实验过程中，温度是通过外部高斯噪声源控制的，该噪声模拟了一个有效的热浴，其温度变化速度比系统的任何弛豫时间都快。