Mechanical Engineering, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.
Phys Rev Lett. 2018 Jun 22;120(25):250602. doi: 10.1103/PhysRevLett.120.250602.
Inverted quantum states provide a challenge to classical thermodynamics, since they appear to contradict the classical formulation of the second law of thermodynamics. Ramsey interpreted these states as stable equilibrium states of negative thermodynamic temperature, and added a provision to allow these states to the Kelvin-Planck statement of the second law [N. F. Ramsey, Phys. Rev. 103, 20 (1956)PHRVAO0031-899X10.1103/PhysRev.103.20]. Since then, Ramsey's interpretation has prevailed in the literature. Here, we present an alternative option to accommodate inverted states within thermodynamics, which strictly enforces the original Kelvin-Planck statement of the second law, and reconciles inverted states and the second law by interpreting the former as unstable states, for which no temperature-positive or negative-can be defined. Specifically, we recognize inverted quantum states as temperature-unstable states, for which all processes are in agreement with the original Kelvin-Planck statement of the second law, and positive thermodynamic temperatures in stable equilibrium states. These temperature-unstable states can only be created by work done to the system, which is stored as energy in the unstable states, and can be released as work again, just as in a battery or a spring.
反演量子态对经典热力学提出了挑战，因为它们似乎与经典热力学第二定律的表述相矛盾。拉姆齐将这些态解释为负热力学温度的稳定平衡态，并在允许这些态存在的条件下，对开尔文-普朗克表述的热力学第二定律做出了补充[拉姆齐，《物理评论》103,20（1956）]。从那时起，拉姆齐的解释就在文献中占据了主导地位。在这里，我们提出了一种在热力学中容纳反演态的替代方案，该方案严格执行开尔文-普朗克表述的热力学第二定律，并通过将反演态解释为不稳定态来协调反演态和热力学第二定律，对于不稳定态，无法定义正或负的温度。具体来说，我们将反演量子态视为温度不稳定态，所有过程都与热力学第二定律的原始开尔文-普朗克表述一致，而在稳定平衡态中则存在正热力学温度。这些温度不稳定态只能通过对系统做功来产生，这些功被储存在不稳定态中，并可以再次作为功释放出来，就像在电池或弹簧中一样。
