Unitary Renormalizaton Group on Bose-Fermi Kondo Model

Mounica, Mahankali (2021) Unitary Renormalizaton Group on Bose-Fermi Kondo Model. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Mahankali Mounica (16MS134)) 16MS134_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Bose-Fermi Kondo (BFK) Model is an extension of the Kondo model where the impurity interacts with a bosonic bath along with the fermionic bath. At low temperature, this interaction forces the impurity to stay in one spin state detering the formation of the singlet thereby interfering with the kondo screening cloud. This competition of forces means that there is a phase transition marking the boundary between fermionic, bosonic dominant regimes which has been confirmed through perturbative RG calculations. The goal of this project is to understand the BFK model through a non-perturbative RG formalism called Unitary Renormalization Group (URG). In combination with lang-firsov transformations, the anti-ferromagnetic SU (2) invariant impurity-boson interaction is reduced to a bosonic field coupled to the impurity spin. As a simpler model, we then consider the scaling behaviour of the Kondo model where the impurity is coupled to a magnetic field.

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