Quantum Monte Carlo study of thermodynamic properties of low-dimensional quantum spin systems

直道 羽田野

Seiji Miyashita, Shoji Yamamoto, Tota Nakamura

Anders W. Sandvik, Elbio R. Dagotto, Douglas J. Scalapino

J. W. Lyklema

An exact Monte Carlo method for calculating thermodynamic properties of quantum spin systems is described. Results for one-dimensional ferromagnetic and antiferromagnetic systems and for three-dimensional ferromagnetic systems show that the method can be used to study quantum spin systems as extensively as classical spin systems are studied with conventional Monte Carlo methods.

Tota Nakamura, Yôhei Saika

A one-dimensional fully frustrated quantum spin system called the Δ -chain is investigated, particularly with respect to the low-temperature structure of the specific heat, by quantum Monte Carlo simulations using the restructuring method. Sizes of the systems we considered are N =32,48 and 64. The simulation results together with the diagonalization results for N =10 and 16 show that the size dependence of the data is very weak, and thus the second peak of the specific heat stably exists at T <0.1, which corresponds to less than half the spin gap. Locality of excitations is seen in the Monte Carlo snapshot. We consider that the low-temperature properties of this system are governed by the local elementary excitations which generate the Schottky-type specific heat peak in the background of the ordinary thermal specific heat.

貴則 杉本