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Low-energy effective field theory investigation of lightly doped antiferromagnets

Florian Kämpfer **MIT**
__Abstract:__
In this seminar I will try to give you some flavor of what I have been doing during my PhD work. I will concentrate on the analytic part where, based on Hubbard-type models, we have constructed a low-energy effective field theory for lightly doped antiferromagnets. This effective theory is a condensed matter analog of Baryon Chiral Perturbation theory for QCD which is extremely successful in describing the low-energy physics of QCD. In the first part of the talk I will explain the symmetry based construction of the theory for electron or hole doped antiferromagnets. In the second part I will apply the effective theory to the problem of two isolated holes (or electrons) in an otherwise undoped system and we will examine magnon-mediated binding between two fermions. At the end I will discuss the case of a finite but small density of fermions doped in the antiferromagnet. Our analysis is restricted to homogeneous fermion densities and we will examine possible ground state configurations of the staggered magnetization vector.