Nonperturbative saddle point for the effective action of disordered and interacting electrons in 2D.
We find a nonperturbative saddle-point solution for the nonlinear sigma model proposed by Finkelstein for interacting and disordered electronic systems. Spin rotation symmetry, present in the original saddle-point solution, is spontaneously broken at one loop, as in the Coleman-Weinberg mechanism. The new solution is singular in both the disorder and triplet interaction strengths, and it also explicitly demonstrates that a nontrivial ferromagnetic state appears in a theory where the disorder average is carried out from the outset.
Chamon
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Department of Physics, Boston University, Boston, Massachusetts, USA.
Mucciolo
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