| Summary: | Quantum Monte Carlo simulations provide one of the more powerful and
versatile numerical approaches to condensed matter systems. However, their
application to frustrated quantum spin models, in all relevant temperature
regimes, is hamstrung by the infamous "sign problem." Here we exploit the fact
that the sign problem is basis-dependent. Recent studies have shown that
passing to a dimer (two-site) basis eliminates the sign problem completely for
a fully frustrated spin model on the two-leg ladder. We generalize this result
to all partially frustrated two-leg spin-1/2 ladders, meaning those where the
diagonal and leg couplings take any antiferromagnetic values. We find that,
although the sign problem does reappear, it remains remarkably mild throughout
the entire phase diagram. We explain this result and apply it to perform
efficient quantum Monte Carlo simulations of frustrated ladders, obtaining
accurate results for thermodynamic quantities such as the magnetic specific
heat and susceptibility of ladders up to L=200 rungs (400 spins 1/2) and down
to very low temperatures.
|
|---|
