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

In this paper I present a Quantum Monte Carlo (QMC) study of the magnetic properties of an anti-ferromagnetic spin ladder (C5H12N)(2)CuBr4. 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 Delta =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. (C) 2016 Elsevier Ltd. All rights reserved.