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**KOÇ UNIVERSITY PHYSICS SEMINAR**

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**Speaker ** : Menderes Işkın, Koç University

**Title ** : BCS theory of time-reversal-symmetric Hofstadter-Hubbard model

**Date ** : May 9, 2017 Tuesday

**Time** : 4:00 P.M.

**Cookie & Tea** : SCI 103 3:45 P.M.

**Place** : SCI 103

**Abstract:
**The competition between the length scales associated with the periodicity of a lattice potential and the cyclotron radius of a uniform magnetic field is known to have dramatic effects on the single-particle properties of a quantum particle, e.g., the fractal spectrum is known as the Hofstadter butterfly. Having this intricate competition in mind, we consider a two-component Fermi gas on a square optical lattice with opposite synthetic magnetic fields for the components, and study its effects on the many-body BCS-pairing phenomenon. By a careful addressing of the distinct superfluid transitions from the semi-metal, quantum spin-Hall insulator or normal phases, I will talk about the low-temperature phase diagrams of the model, displaying lobe structures that are reminiscence of the well-known Mott-insulator transition of the Bose-Hubbard model.