Microscopic theories of solid 4He: when is Bose-Einstein present?
Luciano Reatto
Université de Milan
Mon, May. 14th 2007, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
In the search of the supersolid state of matter properties of solid 4He have been computed by simulation methods for realistic hamiltonians of the system both in the ground state and at finite temperatures. In the talk I shall mainly discuss T=0 K results obtained with variational methods and with the "exact" path integral ground state method. We aim at giving answer to the following basic questions: \begin{itemize} \item Is the ground state of bulk solid 4He a commensurate crystal (no zero point vacancies) or is it incommensurate? \item Do multiple vacancies form a bound state or not? \item Is Bose--Einstein condensation present in the commensurate ground state or BEC can be present only in presence of some sort of disorder (intrinsic or metastable)? \item Are grain boundaries always conducing or not? \end{itemize} Comparison with results obtained at finite temperature with path integral Monte Carlo methods will be presented and the status of experiments commented.