Thermodynamic properties of highly frustrated quantum spin ladders: influence of many-particle bound states

Understand

Quantum antiferromagnets have proven to be some of the cleanest realizations available for theoretical, numerical, and experimental studies of quantum fluctuation effects.

• At finite temperatures, however, the additional effects of thermal fluctuations in the restricted phase space of a low-dimensional system have received much less attention, particularly the situation in frustrated quantum magnets, where the excitations may be complex collective (bound or even fractionalized) modes.
• We investigate this problem by studying the thermodynamic properties of the frustrated two-leg S=1/2 spin ladder, with particular emphasis on the fully frustrated case.
• We present numerical results for the magnetic specific heat and susceptibility, obtained from exact diagonalization and quantum Monte Carlo studies, which we show can be rendered free of the sign problem even in a strongly frustrated system and which allow us to reach unprecedented sizes of L=200 ladder rungs.