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Quantum Monte Carlo simulations of complex lattice Hamiltonians

Event Details

Event Dates: 

Monday, August 18, 2014 - 12:00pm

Seminar Location: 

  • JILA X325

Speaker Name(s): 

Dr. Valéry Rousseau

Speaker Affiliation(s): 

Louisiana State University
Seminar Type/Subject

Scientific Seminar Type: 

  • JILA Public Seminar

Event Details & Abstract: 

After several decades of numerical studies of the Hubbard model in its simplest forms, the interest for this model has evolved to more complex forms, as well for fermions as for bosons. These new forms of the Hubbard model are challenging for most quantum Monte Carlo (QMC) methods. I will present the Stochastic Green Function (SGF) algorithm, which is an exact continuous-time QMC method that can be applied to any sign-problem-free lattice Hamiltonian. I will review the concept of superfluidity and point to some common misconceptions. In particular, I will show that the well-known formulae that allow one to calculate the superfluid density are valid only for a restricted class of Hamiltonians. I will derive a general formula that can be applied in all cases. Finally, I will apply these ideas to a model of bosons on a kagome lattice with sextic ring-exchange interactions, which is believed to exhibit a normal Bose-liquid at zero-temperature.