title: Spin-Peierls transition in low-dimensional quantum spin systems: a Green's function approach.
abstract: We study the spin-Peierls (SP) transition of one-dimensional chain polymeric complexes coupled to lattice by means of many-body Green's function theory. The chain effective elastic constant is an intrinsic factor that determines the order of SP transition. It is found that the SP transition temperature T(SP) and the susceptibility-maximum temperature T(max) are in agreement with the experimental results. When an external magnetic field is applied to the chain, it makes T(SP) and T(max) decrease, and drives the SP transition from the second order to the first order. Besides, we show that the two-site thermal entanglement entropy is a good indicator of SP transition. Further considering the effect of interchain coupling on SP transition, with weak coupling of double-chain, the theoretical values are closer to the experimental results. We also calculate the density of states and spectral functions, which show that the energy gap vanishes at a critical temperature lower than T(SP), indicating a gapless SP phase lies in the gapped dimerized phase. The interchain coupling can drive the SP transition from the second order to the first order, while the SP dimerization may collapse for large interchain couplings.
authors.affiliation: School of Physics and Wuhan High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: L J
authors.initials: LJ
authors.lastname: Ding
authors.forename: K L
authors.initials: KL
authors.lastname: Yao
authors.forename: H H
authors.initials: HH
authors.lastname: Fu