Ground-state phase diagram and thermodynamics of coupled trimer chains

Article

关键词: DIMENSIONAL HEISENBERG-FERROMAGNET;    ANTIFERROMAGNETIC UNIFORM;    CRITICAL-BEHAVIOR;    SPIN CHAINS;    SUSCEPTIBILITY;    SPECTRUM;    MODEL;   

DOI  :  10.1103/PhysRevB.105.134423

来源: SCIE

【 摘 要 】

The density matrix renormalization group and quantum Monte Carlo methods are used to describe coupled trimer chains in a magnetic field h. The Hamiltonian contains exchange terms involving the intratrimer coupling J(1) (taken as the unit of energy) and the intertrimer coupling J(2), plus the Zeeman interaction for a magnetic field h along the z direction. Results for the magnetization per trimer m are calculated in regimes of positive and negative values of the ratio J = J(2)/J(1), from which the rich field-induced ground state phase diagram h versus J is derived, with the presence of a Luttinger liquid, the 1/3 plateau (m = 1/2), and the one of fully polarized magnetization (m = 3/2). Also, zero-field Lanczos calculation of the spin-wave dispersion from the 1/3 plateau for S-z = 1 is shown at the previous regimes of J values. In addition, we also report on the decay of correlation functions of trimers along open chains, as well as the average two-magnon distribution. The ground state is ferrimagnetic for 0 < J <= 1, and is a singlet for -1 <= J < 0. In the singlet phase, the spin correlation functions along the legs present an antiferromagnetic power-law decay, similar to the spin-1/2 linear chain, thus suggesting that the ground state is made of three coupled antiferromagnetically oriented chains. In the singlet phase, the dimensionless thermal magnetic susceptibility per site normalized by 1/vertical bar J vertical bar gets closer to 1/pi(2) as the temperature T -> 0. For the ferrimagnetic phase, we fit the susceptibility to the experimental data for the compound Pb3Cu3(PO4)(4) and estimate the model exchange couplings: J(1) = 74.8 K and J = 0.4. These values imply a range of energies for the magnon excitations that are in accord with the data from neutron scattering experiments on Pb3Cu3(PO4)(4) for two excitation modes. The 1/3 plateau closes only at 1/vertical bar J vertical bar = 0 with J < 0.

【 授权许可】

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