Előadó: Halász Gábor (SZFI)
Az előadás témája: Theory of the Kitaev model in a  magnetic field
Az előadás időpontja: 2021. május 25., 14 óra
Helyszín: videokonferencia, a video linkje: https://teams.microsoft.com/l/meetup-join/19%3ace423c05cd1543ab9f9905886590ad69%40thread.tacv2/1620042537966?context=%7b%22Tid%22%3a%224d7ddeef-14ff-4911-8c11-401c69384d77%22%2c%22Oid%22%3a%22969d2d4a-5ba8-43f1-bd69-93f0998b025f%22%7d
Recent numerical studies indicate that the antiferromagnetic Kitaev honeycomb lattice model undergoes a magnetic-field-induced quantum phase transition into a new spin-liquid phase. This intermediate-field phase has been previously characterized as a gapless spin liquid. By implementing a recently developed variational approach based on the exact fractionalized excitations of the zero-field model, we demonstrate that the field-induced spin liquid is gapped and belongs to Kitaev's 16-fold way. Specifically, the low-field non-Abelian liquid with Chern number C=±1 transitions into an Abelian liquid with C=±4. The critical field and the field-dependent behaviors of key physical quantities are in good quantitative agreement with published numerical results. Furthermore, we derive an effective field theory for the field-induced critical point which readily explains the ostensibly gapless nature of the intermediate-field spin liquid.