2001/06/21 by Yasushi Honda, Honda, Yasushi, Tsuyoshi Horiguchi +1
Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum many-body systems #Statistical Mechanics (cond-mat.stat-mech) #cond-mat.mtrl-sci #cond-mat.stat-mech
paper · pdf · doi:10.48550/arxiv.cond-mat/0106426
12 pages, 14 figures
arxiv created 2001/06/21 · openalex publication_date 2001/06/21 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We investigate an S=1/2 two-leg spin ladder with a cyclic four-spin exchange interaction whose interaction constant is denoted by J4, by using the density matrix renormalization group method. The interchain and the intrachain interaction constant are denoted by Jrung and J\rm leg, respectively and assumed to be antiferromagnetic. It turns out that a spin gap between the singlet (Stotz=0) and the triplet (Stotz=1) states vanishes at J4/Jleg ≃ 0.3 for Jrung=Jleg. This result is in contrast with the fact that the S=1/2 antiferromagnetic Heisenberg ladder, that is the case of Jrung ≠ Jleg, J4=0, has a spin gap for all nonzero value of interchain interaction J\rm rung>0. We find a larger value of the correlation length for the spin-pair correlation function than a linear size L of the system at J4/J\rm leg=0.3 and Jrung=Jleg: the correlation length ξ is about 204 times of the lattice constant for L=84 for these values of interactions. We also find that the string correlation function decays rather algebraically than exponentially at J4/Jleg=0.3 and Jrung=Jleg. These results suggest that there is a quantum phase transition at J4/Jleg ≃ 0.3 for Jrung=Jleg. We estimate a phase boundary where the spin gap vanishes in a J4/Jleg-Jrung/Jleg plane and obtain a consistent result with that by a perturbation theory for J\rm rung/Jleg>1.