Abstract
The density matrix renormalization group and quantum Monte Carlo methods are used to describe coupled trimer chains in a magnetic field . The Hamiltonian contains exchange terms involving the intratrimer coupling (taken as the unit of energy) and the intertrimer coupling , plus the Zeeman interaction for a magnetic field along the direction. Results for the magnetization per trimer are calculated in regimes of positive and negative values of the ratio , from which the rich field-induced ground state phase diagram versus is derived, with the presence of a Luttinger liquid, the 1/3 plateau (), and the one of fully polarized magnetization (). Also, zero-field Lanczos calculation of the spin-wave dispersion from the 1/3 plateau for is shown at the previous regimes of 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 , and is a singlet for . 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 gets closer to as the temperature . For the ferrimagnetic phase, we fit the susceptibility to the experimental data for the compound and estimate the model exchange couplings: and . These values imply a range of energies for the magnon excitations that are in accord with the data from neutron scattering experiments on for two excitation modes. The 1/3 plateau closes only at with .
3 More- Received 1 January 2022
- Revised 22 March 2022
- Accepted 11 April 2022
DOI:https://doi.org/10.1103/PhysRevB.105.134423
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