Miotti Marcos, Martins Edmur Braga, Hemmerling Michał, Bagnato Vanderlei Salvador
São Carlos Institute of Physics, University of São Paulo, São Carlos 13566-590, Brazil.
Biomedical Engineering Department, Texas A&M University, College Station, TX 77843, USA.
Entropy (Basel). 2024 Jul 31;26(8):658. doi: 10.3390/e26080658.
Quantum thermal engines have received much attention in recent years due to their potential applications. For a candidate group, harmonically trapped gases under Bose-Einstein condensation (BEC), we see little investigation on the energy transference around that transition. Therefore, we present an empirical study with rubidium-87 gas samples in a magnetic harmonic trap. We developed an empirical equation of state model to fit to our experimental dataset, expressing the pressure parameter in terms of temperature, and six technical coefficients, functions of the volume parameter and the number of atoms. By using standard thermodynamic relations, we determine the system's entropy, shown to be constant at the BEC transition, as expected. Being isentropic makes the BEC transition an energy source for non-mechanical work. Hence, we observed that the enthalpy at the BEC transition, at fixed values of the volume parameter, grows fairly linearly with the number of atoms. We fitted a linear function to that data, finding the specific enthalpy of the BEC transformation and the intrinsic enthalpic loss for BEC. We deem this study to be a step closer to practical quantum-based engines.
近年来，量子热机因其潜在应用受到了广泛关注。对于一个候选体系，即处于玻色 - 爱因斯坦凝聚（BEC）状态下的简谐捕获气体，我们发现关于该转变附近能量转移的研究很少。因此，我们对处于磁谐波陷阱中的铷 - 87气体样本进行了实证研究。我们开发了一个状态方程的经验模型来拟合我们的实验数据集，该模型用温度以及六个技术系数（体积参数和原子数的函数）来表示压力参数。通过使用标准热力学关系，我们确定了系统的熵，正如预期的那样，该熵在BEC转变时保持恒定。等熵性使得BEC转变成为非机械功的能量来源。因此，我们观察到在体积参数固定值下，BEC转变时的焓随原子数大致呈线性增长。我们对该数据拟合了一个线性函数，从而得到了BEC转变的比焓和BEC的固有焓损失。我们认为这项研究向基于量子的实用发动机又迈进了一步。
