Shell-Model Monte Carlo Simulations of Pairing in Few-Fermion Systems

Physics Division, Oak Ridge National Laboratories, Oak Ridge, TN 37831, USA(Dated: August 4, 2008)We study a trapped system of fermions with an attractive zero-range two-body interaction usingthe Shell-Model Monte Carlo method. The method provides ab initio results in the low N limitwhere mean-field theory is not applicable. The energy and pairing properties are presented asfunctions of interaction strength, particle number, and temperature. In the interesting region wheretypical matrix elements of the two-body interaction are comparable to the level spacing of the trapwe find large odd-even effects and signatures of shell structure. As a function of temperature, weobserve the disappearance of these effects as in a phase transition.