Programme

P.65 -- Poster, NCTP-43

Date: Wednesday, 1 August 2018

Time: 08:30 - 10:00

Fermionized Heisenberg model on a non - Bravais lattice: Exact local constraint

Pham Thi Thanh Nga (a), Vu Kim Thai (b), and Nguyen Toan Thang (c)

(a) Thuy loi University, 175 Tay Son, Hanoi; (b) University of Economic and Technical Industries, 456 Minh Khai, Hanoi; (c) Institute of Physics, 10 Dao Tan, Hanoi;

We study magnetic orders of the Heisenberg model on a non-Bravais lattice bassed on the Popov - Fedotov trick for exactly treating the local constraint on on-site spin number. The spin operators are represented by auxiliary fermions and an imaginary chemical potential is introduced. The following steps are performed: i) Classical ground state is parameterized by a magnetic ordering vector and angles between the spins within a unit cell. ii) Going to a local coordinate system. ii) Using functional integral representation for partition function and calculating determinants of block matrices by Powel method. We obtain general formulae for sublattice magnetization, free energy and other thermo-dynamical quantities for non - Bravais lattice structures in magnetically ordered phases in the framework of one loop approximation. For illustration we obtain some explicit expressions for a honeycomb lattice and compare them with the slave results.

Presenter: Pham Thi Thanh Nga