Quantum magnetism

Quantum Magnetism in Strongly Correlated Electron Systems

Problems of strongly interacting electrons can be greatly simplified by reducing them to effective quantum spin models. The initial step is renormalization of the Hamiltonian into a lower energy subspace which mimics the physics of the interested degrees of freedom. The Hubbard model is the so called parent Hamiltonian in this field. It is defined on a lattice by a kinetic (hopping; t) term in addition to a columb on-site interaction (U) for electrons. In the case of large columb interaction the double site occupation is not favored and should be projected out. This leads to the t-J model which has 3 degrees of freedom for each lattice site and consists of the kinetic and exchange terms. If we further consider the half-filling electron density the t-J model will be trasformed to the well known Heisenberg model. The Heisenberg model and its extended forms have a broad application to explain some properties in the theory of high-Tc superconductors, heavy fermions,... simply called "Quantum magnetism".

In this group we are working in some sub-fields of quantum magnetism listed below.

Abdollah Langari (Assoc. Prof. SUT)	Anisotropic Kondo-necklace model, Phase separation in t-J model, Quantum phase transitions
Jahanfar Abouie (Assist. Prof. Shahrood U. )	Correlation effects in ferrimagnetic spin models
Alireza Akbari (Postdoc. Max-Planck Inst. )	Novel magnetic effects at low temperature glasses
Hamed Rezania (Ph. D. Student, SUT)	Green's function approach to the Kondo-necklace model
Rohollah Jafari (Ph. D. Student, IASBS )	Quantum renormalization group and correlation effects in quantum magnetism
Mehdi Kargarian (Ph. D. Student, SUT)	Entanglement and quantum critical properties
Fateme Rostamzadeh (M. Sc. Student, SUT )	Charge transport via a molecular magnet
Mohammad Siahatgar (M. Sc. Student, SUT )	Finite temperature properties of the XXZ model in transverse field

More information can be found in: http://sina.sharif.edu/~langari/