Crystallization in Mass‐Asymmetric Electron‐Hole Bilayers

Abstract

We consider a mass-asymmetric electron and hole bilayer. Electron and hole Coulomb correlations and electron and hole quantum effects are treated on first princles by path integral Monte Carlo methods. For a fixed layer separation we vary the mass ratio M of holes and electrons between 1 and 100 and analyze the structural changes in the system. While, for the chosen density, the electrons are in a nearly homogeneous state, the hole arrangement changes from homogeneous to localized, with increasing M which is verified for both, mesoscopic bilayers in a parabolic trap and for a macroscopic system.

Classical and quantum Coulomb crystals

“…For classical electrons this requires a sufficiently high temperature whereas in a quantum plasma ionization is possible when electron wave functions of neighboring atoms start to overlap; this leads to tunnel ionization ͑Mott effect͒ which occurs at a sufficiently high density. In summary, we find two alternative sets of conditions, 56 which is due to the 2D confinement of the particles.…”

Ground states of finite spherical Yukawa crystals

“…The reason for this behavior is that in all the cases but for N = 57, 58, 60 the new ground state configuration, e.g. (24,6) at screening above κ = 1.5, always forms a platonic body on the inner shell. This is a highly symmetric configuration which obviously decreases the energy per particle better than by just adding one particle [19,34].…”

“…[31,32]. (26,5) and green for (25,6)] and the end [red for (27,4)] of the occurrence of these configurations in the simulations. The inset shows the energy difference per particle for two stable states: the red The simplest fit for the ground state total energy per particle has the form…”

“…For κ < 1.5623 the ground state configuration is (27,4), whereas at κ cr1 = 1.5623 the configuration (26,5) becomes the ground state. Finally, at κ cr2 = 1.6142 this configuration is replaced by (25,6) which remains the ground state for larger κ. This behavior can be seen in the energy differences plotted in the inset of figure 2.…”

“…Coulomb crystal formation is among the most exciting cooperative phenomena in charged particle systems and has been observed in a variety of fields, including ultracold ions in Paul and Penning traps [1]- [3], electrons and excitons in semiconductor quantum dots [4] and bilayers [5,6]. Coulomb crystallization also occurs in classical and quantum two-component systems, such as electron-ion or electron-hole plasmas [7,8] or laser-cooled expanding plasmas [9], for a recent overview see [10,11].…”