Quantum Monte Carlo simulation of antiferromagnetic spin ladder (C5H12N)2CuBr4

Abstract

Abstract In this paper I present a Quantum Monte Carlo (QMC) study of the magnetic properties of an antiferromagnetic spin ladder (C 5 H 12 N) 2 CuBr 4 . This compound is the prototype of the Heisenberg model for a two leg spin ladder in the presence of an external magnetic field. The susceptibility phase diagram has a rounded peak in the vicinity of T =7.4 K, obeys Troyer׳s law for low temperatures, and Curie׳s law for high temperatures. I also study the susceptibility diagram in low temperatures and I found the spin gap Δ =9.26 K, in good concordance with the experimental value, 9.5 K. In high field, I present a diagram of magnetization as a function of temperature. In the vicinity of a critical field, H ci , the magnetization scales with T 1/2 and this result was found also in the QMC simulation. In all the results, there is a very good concordance with the experimental data. I also show in this paper that the spin gap is null and the susceptibility is proportional to T for low temperatures when relatively high values of the ladders’ coupling is taken in account.