The Truncated Polynomial Expansion Monte Carlo Method for Fermion Systems Coupled to Classical Fields: A Model Independent Implementation

摘要

A software library is presented for the polynomial expansion method (PEM) ofthe density of states (DOS) developed by two of the authors (N.F. and Y. M.).The library provides all necessary functions for the use of the PEM and itstruncated version (TPEM) in a model independent way. The PEM/TPEM replaces theexact diagonalization of the one electron sector in models for fermions coupledto classical fields. The computational cost of the algorithm is O(N) -- with Nthe number of lattice sites -- for the TPEM which should be contrasted with thecomputational cost of the diagonalization technique that scales as O(N^4). Themethod is applied for the first time to a double exchange model with finiteHund coupling and also to diluted spin-fermion models.