Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 30: Superconductivity: Poster Session
TT 30.4: Poster
Thursday, September 8, 2022, 15:00–18:00, P1
Microscopic theory of the multi-orbital FFLO phase in the iron-based superconductors — •Luka Jibuti and Ilya Eremin — Institute für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Deutschland
We study the superconducting Frude-Ferrel-Larnik-Ovchinnikov (FFLO) phase, a superconducting phase, where Cooper pairs having non-zero center-of-mass momentum q→, in iron-based superconductors. We develop a microscopic theory model considering two Γ-centered hole pockets created by xz and yz orbitals. We write the low energy effective Hamiltonian of the form Ĥ = Ĥ0 + Ĥint, where the first term includes the kinetic therm, the k→-independent spin orbit coupling and the Zeeman field. We introduce the superconducting pairing between fermions in xz and yz orbitals and we restrict ourselves with the interactions which lead to the inter-band pairing of Cooper pairs. Writing the system Hamiltonian initially in orbital basis allowes us to observe the changes of the orbital weights at the Fermi energy when making the transition from Normal to FFLO phase and pinpoint the direction and value of the center-of-mass momentum q→ that connects particles within the same orbital. From the mean field calculations for magnetic field just above the Pauli limit and for temperatures close to absolute zero, we are able to observe that ±q→ vectors connect particles within yz and xz orbitals respectively. We also observe that q→ is highly dependent on the magnetic field and temperature, and the increase of the SOC constant destroys the FFLO phase.