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Effects of Berry phase and instantons in one dimensional Kondo-Heisenberg model

Motivated by the global phase diagram of antiferromagnetic heavy-fermion metals, we study the Kondo effect from the perspective of a nonlinear sigma model in the one dimensional Kondo-Heisenberg model. We focus on the effects of the instanton configurations of the sigma-model field and the associated Berry phase. Guided by the results derived using bosonization methods, we demonstrate that the Kondo singlet formation is accompanied by an emergent Berry phase. This Berry phase also captures the competition between the Kondo-singlet formation and spin Peierls correlations. Related effects are likely to be realized in Kondo lattice systems in higher dimensions.