Negrete Oscar A, Peña Francisco J, Florez Juan M, Vargas Patricio
Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso 2340000, Chile.
Centro para el Desarrollo de la Nanociencia y la Nanotecnología (CEDENNA), Santiago 8320000, Chile.
Entropy (Basel). 2018 Jul 27;20(8):557. doi: 10.3390/e20080557.
In this work, we report the magnetocaloric effect (MCE) in two systems of non-interactive particles: the first corresponds to the Landau problem case and the second the case of an electron in a quantum dot subjected to a parabolic confinement potential. In the first scenario, we realize that the effect is totally different from what happens when the degeneracy of a single electron confined in a magnetic field is not taken into account. In particular, when the degeneracy of the system is negligible, the magnetocaloric effect cools the system, while in the other case, when the degeneracy is strong, the system heats up. For the second case, we study the competition between the characteristic frequency of the potential trap and the cyclotron frequency to find the optimal region that maximizes the ΔT of the magnetocaloric effect, and due to the strong degeneracy of this problem, the results are in coherence with those obtained for the Landau problem. Finally, we consider the case of a transition from a normal MCE to an inverse one and back to normal as a function of temperature. This is due to the competition between the diamagnetic and paramagnetic response when the electron spin in the formulation is included.
在这项工作中，我们报告了两种非相互作用粒子系统中的磁热效应（MCE）：第一种对应于朗道问题情形，第二种是处于抛物线限制势中的量子点中的电子情形。在第一种情形中，我们认识到该效应与不考虑磁场中单个电子简并性时的情况完全不同。特别是，当系统的简并性可忽略不计时，磁热效应使系统冷却，而在另一种情况下，当简并性很强时，系统升温。对于第二种情况，我们研究势阱的特征频率与回旋频率之间的竞争，以找到使磁热效应的ΔT最大化的最佳区域，并且由于该问题的强简并性，结果与朗道问题所获得的结果一致。最后，我们考虑作为温度函数的从正常磁热效应到逆磁热效应再回到正常磁热效应的转变情况。这是由于在公式中包含电子自旋时抗磁和顺磁响应之间的竞争所致。
