Japan Science and Technology Agency, Exploratory Research for Advanced Technology (ERATO), Macroscopic Quantum Control Project, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
Science. 2010 Jan 22;327(5964):442-5. doi: 10.1126/science.1183012.
Thermodynamic properties of matter generally depend on the details of interactions between its constituent parts. However, in a unitary Fermi gas where the scattering length diverges, thermodynamics is determined through universal functions that depend only on the particle density and temperature. By using only the general form of the equation of state and the equation of force balance, we measured the local internal energy of the trapped gas as a function of these parameters. Other universal functions, such as those corresponding to the Helmholtz free energy, chemical potential, and entropy, were calculated through general thermodynamic relations. The critical parameters were also determined at the superfluid transition temperature. These results apply to all strongly interacting fermionic systems, including neutron stars and nuclear matter.
物质的热力学性质通常取决于其组成部分相互作用的细节。然而，在散射长度发散的单粒子费米气体中，热力学是由仅依赖于粒子密度和温度的普适函数决定的。我们仅使用状态方程和力平衡方程的一般形式，测量了被俘获气体的局域内能作为这些参数的函数。其他普适函数，如对应于亥姆霍兹自由能、化学势和熵的函数，是通过一般热力学关系计算出来的。在超流转变温度处也确定了临界参数。这些结果适用于所有强相互作用的费米子系统，包括中子星和核物质。
