Thursday meeting

[Cond.Matt. & Stat.Mech.Section]

Condensed Matter Physics Associates' Meeting


" Canonical representation for electrons and  its application to the Hubbard model"
 
 Speaker: Brijesh  KUMAR
(Jawaharlal Nehru University, New Delhi)
 _______________________________________________ 
  
Time: 11:30 hours 

Venue: Luigi Stasi Seminar Room (first floor, Leonardo Building)

Date: Thursday, 15 July 2010



Abstract

A new representation for electrons is introduced, in which the electron operators are written in terms of a spinless fermion and the Pauli operators.  This representation is canonical, invertible, and constraint-free. Importantly, it simplifies the Hubbard interaction.  On a bipartite lattice, the Hubbard model is reduced to a form in which the exchange interaction emerges by decoupling the Pauli subsystem from the spinless fermion bath, and correctly reproduces the large U superexchange.  In this representation, the in*nite-U Hubbard problem acquires an elegant from, and provides a nice Hamiltonian description of the Nagaoka ferromagnetism on bipartite lattices.  Interestingly, the ferromagnetism in the Hubbard model is related to the gauge invariance of the spinless fermions. In one-dimension, the infinite-U Hubbard model is exactly solved by an approach different from the Bethe Ansatz.  This method also solves a realistic spin-orbital model, and a general class of 1d models.

 References: [1] B. Kumar, PHYSICAL REVIEW B 77, 205115 (2008)


                     [2] B. Kumar, PHYSICAL REVIEW B 79, 155121 (2009

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