Density Profiles in a Quantum Coulomb Fluid Near a Hard Wall

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• 作者：J.-N. Aqua and F. Cornu
• 关键词：Coulomb interactions ; quantum mechanics ; hard wall ; grand ; canonical ensemble ; inhomogeneous Debye equation ; surface charge
• 刊名：Journal of Statistical Physics
• 出版年：2004
• 出版时间：2004
• 年：2004
• 卷：115
• 期：3/4
• 页码：997-1036
• 全文大小：482 KB
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics
  Statistical Physics
  Mathematical and Computational Physics
  Physical Chemistry
  Quantum Physics
  
• 出版者：Springer Netherlands
• ISSN：1572-9613

文摘

Equilibrium particle densities near a hard wall are studied for a quantum fluid made of point charges which interact via Coulomb potential without any regularization. In the framework of the grand-canonical ensemble, we use an equivalence with a classical system of loops with random shapes, based on the Feynman–Kac path-integral representation of the quantum Gibbs factor. After systematic resummations of Coulomb divergences in the Mayer fugacity expansions of loop densities, there appears a screened potential . It obeys an inhomogeneous Debye–Hückel equation with an effective screening length which depends on the distance from the wall. The formal solution for can be expanded in powers of the ratios of the de Broglie thermal wavelengths ''s of each species and the limit of the screening length far away from the wall. In a regime of low degeneracy and weak coupling, exact analytical density profiles are calculated at first order in two independent parameters. Because of the vanishing of wave-functions close to the wall, density profiles vanish gaussianly fast in the vicinity of the wall over distances ''s, with an essential singularity in Planck constant . When species have different masses, this effect is equivalent to the appearance of a quantum surface charge localized on the wall and proportional to at leading order. Then, density profiles, as well as the electrostatic potential drop created by the charge-density profile, also involve a term linear in and which decays exponentially fast over the classical Debye screening length _D. The corresponding contribution to the global surface charge exactly compensates the charge in the very vicinity of the surface, so that the net electric field vanishes in the bulk, as it should.