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5 results on '"FFLO phase"'

1. Disordered structures in ultracold spin-imbalanced Fermi gas

Author

Buğra Tüzemen, Tomasz Zawiślak, Gabriel Wlazłowski, and Piotr Magierski

Subjects
quantum gases, spin-imbalanced ultracold Fermi gas, FFLO phase, supersolidity, Science, Physics, QC1-999
Abstract

We investigate properties of spin-imbalanced ultracold Fermi gas in a large range of spin polarizations at low temperatures. We present results of microscopic calculations based on mean-field and density functional theory approaches, with no symmetry constraints. At low polarization values we predict the structure of the system as consisting of several spin-polarized droplets. As the polarization increases, the system self-organizes into a disordered structures similar to liquid crystals, and energetically they can compete with ordered structures such as grid-like domain walls. At higher polarizations the system starts to develop regularities that, in principle, can be called supersolid, where periodic density modulation and pairing correlations coexist. The robustness of the results has been checked with respect to temperature effects, dimensionality, and the presence of a trapping potential. Dynamical stability has also been investigated.

Published
2023
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2. Fulde–Ferrell superfluids in spinless ultracold Fermi gases

Author

Zhen-Fei Zheng, Guang-Can Guo, Zhen Zheng, and Xu-Bo Zou

Subjects
ultracold Fermi gases, BCS theory, FFLO phase, 67.85.-d, 03.75.Ss, 74.20.Fg, Science, Physics, QC1-999
Abstract

The Fulde–Ferrell (FF) superfluid phase, in which fermions form finite momentum Cooper pairings, is well studied in spin-singlet superfluids in past decades. Different from previous works that engineer the FF state in spinful cold atoms, we show that the FF state can emerge in spinless Fermi gases confined in optical lattice associated with nearest-neighbor interactions. The mechanism of the spinless FF state relies on the split Fermi surfaces by tuning the chemistry potential, which naturally gives rise to finite momentum Cooper pairings. The phase transition is accompanied by changed Chern numbers, in which, different from the conventional picture, the band gap does not close. By beyond-mean-field calculations, we find the finite momentum pairing is more robust, yielding the system promising for maintaining the FF state at finite temperature. Finally we present the possible realization and detection scheme of the spinless FF state.

Published
2018
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3. The ab initio study of unconventional superconductivity in CeCoIn5 and FeSe

Author

Andrzej Ptok, Konrad J Kapcia, Przemysław Piekarz, and Andrzej M Oleś

Subjects
ab initio, DFT, superconductivity, FFLO phase, pair susceptibility, 74.20.Pq, Science, Physics, QC1-999
Abstract

The electronic structure and shape of the Fermi surface are known to be of fundamental importance for the superconducting instability in real materials. We demonstrate that such an instability may be explored by static Cooper pair susceptibility renormalized by pairing interaction and present an efficient method of its evaluation using Wannier orbitals derived from ab initio calculation. As an example, this approach is used to search for an unconventional superconducting phase of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) type in a heavy-fermion compound CeCoIn _5 and an iron-based superconductor FeSe. The results suggest that the FFLO superconducting phase occurs at finite magnetic field in both materials.

Published
2017
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4. Spontaneous appearance of the spin-triplet Fulde-Ferrell-Larkin-Ovchinnikov phase in a two-band model : possible application to LaFeAsO_{1-x}F_{x}

Author

M. Zegrodnik and Jozef Spałek

Subjects
Physics, Superconductivity, Condensed Matter::Quantum Gases, Condensed matter physics, unconventional superconductivity, FFLO phase, Fermi surface, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Fulde–Ferrell–Larkin–Ovchinnikov phase, Momentum, Quantum mechanics, Pairing, Condensed Matter::Superconductivity, iron pnictides, Cooper pair, Spin (physics), Phase diagram
Abstract

The possibility of a spontaneous spin-triplet paired phase of the Fulde-Ferrell-Larkin-Ovchinnikov type is studied. As it is shown in a system with the dominant interband pairing and two distinct Fermi surface sheets, the Fermi wave-vector mismatch can be compensated by a nonzero center-of-mass momentum of the Cooper pairs. This idea is examined with the use of a model which describes the two hole-like bands in the iron-based superconductor. It is shown that for the proper range of model parameters, the minima of the free energy appear which correspond to a nonzero Cooper pair momentum. Different superconducting gap symmetries are analyzed, and the corresponding phase diagrams are shown.

Published
2015

5. Role of crystal anisotropy on the vortex state in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase

Author

Alexandre I. Buzdin, Jean-Pascal Brison, Dmitry Denisov, Vu Hung Dao, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), University of Amsterdam [Amsterdam] (UvA), Laboratoire Ondes et Matière d'Aquitaine (LOMA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Instrumentation, Material and Correlated Electrons Physics (IMAPEC), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ANR-09-BLAN-0146,SINUS(2009), ANR-12-BS10-0014,electroVORTEX,Des nanosondes ultra-sensibles pour explorer les distributions de charges électriques dans les supraconducteurs(2012), European Project: 246937,EC:FP7:PEOPLE,FP7-PEOPLE-2009-IRSES,SIMTECH(2010), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), and Van der Waals-Zeeman Institute

Subjects
Vortex state, FFLO phase, Critical field, Critical points, 02 engineering and technology, Tricritical point, 01 natural sciences, Angular dependence, Field orientation, Quantum mechanics, Condensed Matter::Superconductivity, 0103 physical sciences, Crystal anisotropy, 010306 general physics, Anisotropy, S-wave superconductors, Landau levels, Superconductivity, Physics, Condensed Matter::Quantum Gases, Fulde-Ferrell-Larkin-Ovchinnikov phase, Condensed matter physics, Fermi surface, Landau quantization, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Fulde–Ferrell–Larkin–Ovchinnikov phase, PACS : 74.81.-g, 74.25.Dw, 74.25.Op, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Elliptical Fermi surface, Magnetic field, Mixed states, Superconducting critical field, 0210 nano-technology, Mixed state
Abstract

International audience; We demonstrate that the vortex state in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase may be very different depending on the field orientation relative to the crystalline axes. We numerically calculate the upper critical field near the tricritical point taking into account the modulation of the order parameter along the magnetic field as well as the higher Landau levels. For s-wave superconductors with the anisotropy described by an elliptical Fermi surface, we propose a general scheme for the analysis of the angular dependence of the upper critical field at all temperatures on the basis of an exact solution for the order parameter. Our results show that the transitions (with tilting magnetic field) between different types of mixed states may be a salient feature of the FFLO phase.

Published
2013
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