Theoretical Condensed Matter Physics Seminar

2 p.m., Thursday, June 21, 2001
Room 1304, Physics Building

 Spin fluctuations and pseudo-gap in the 2D Hubbard model

Nicolas Dupuis

(Laboratoire de Physique des Solides, Orsay, France)

Abstract:  In the strong-coupling limit, the Hubbard model reduces to the Heisenberg model.  In the low-energy limit, the latter can be mapped onto a non-linear sigma model (NLSM).  We show that spin fluctuations in the Hubbard model can be described by a NLSM both in the weak and strong-coupling regimes.   Solving the NLSM within a "large N" approximation, we show that the system is always disordered at finite temperature with an exponentially large magnetic correlation length at low temperature (renormalized classical regime).  Finally, in the weak-coupling regime, we discuss the absence of quasi-particles and the existence of a pseudo-gap within a one-loop approximation.  Our results are compared to other (weak-coupling) approaches such as FLEX or the two-particle self-consistent theory.
Host:  Victor Yakovenko
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