Quantum orientational melting and the phase diagram of a mesoscopic system

The "phase diagram" of a two-dimensional mesoscopic system of bosons is investigated. An example of such a system is a system of indirect magnetoexcitons in semiconductor double quantum dots. Quantum Monte Carlo calculations show the existence of quantum orientational melting. At zero (quite low) temperature, as quantum fluctuations of the particles intensify, two quantum disordering phenomena occur with increasing de Boer parameter q. First, at q approximate to 10(-3) the system passes to a radially ordered but orientationally disordered state, where different shells of a cluster rotate relative to one another. Then at q approximate to 0.16 a transition to a superfluid state occurs. (C) 1998 American Institute of Physics. [S0021-3640(98)00723-3].