Magnetic impurities at quantum critical points: Large-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>N</mml:mi></mml:math> expansion and connections to symmetry-protected topological states

Abstract

Motivated by recent studies of symmetry protected topological states that are stabilized even in the absence of an energy gap, the authors study analytically the interaction of a (0+1)$D$ impurity spin, which in some cases may be viewed as a topological state bound to a lattice defect, with a (2+1)$D$ strongly interacting bulk, composed of bosonic excitations tuned to a quantum critical point. The question of whether the spin is (partially) screened is addressed within the framework of four different models, using mainly the large-$N$ technique. The authors also point out intriguing connections with the physics of the Sachdev-Ye-Kitaev model.

Topics & Concepts