Fulde-Ferrell state in heavy-fermion superconductors

Yin, Guimei; Maki, Kazumi

doi:10.1103/physrevb.48.650

Cited by 34 publications

(11 citation statements)

References 11 publications

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“…In these materials, a possible existence of the FFLO state has been suggested by a number of groups. 11,12,16,17 For the following discussion, the physical parameters related to the FFLO transition in the normal and superconducting states of these materials are listed in Table I. 4.1 CeRu 2 and UPd 2 Al 3 : is the peak effect a signature of the FFLO state? CeRu 2 is a superconducting cubic Laves phase compound with T c = 6.1 K. Since its discovery in 1958, CeRu 2 had been believed to be a conventional s-wave type-II superconductor.…”

Section: Possible Fflo State In Heavy Fermion Superconductorsmentioning

confidence: 99%

Fulde–Ferrell–Larkin–Ovchinnikov State in Heavy Fermion Superconductors

2007

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The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a novel superconducting state in a strong magnetic field characterized by the formation of Cooper pairs with nonzero total momentum (k ↑, −k + q ↓), instead of the ordinary BCS pairs (k ↑, −k ↓). A fascinating aspect of the FFLO state is that it exhibits inhomogeneous superconducting phases with a spatially oscillating order parameter and spin polarization. The FFLO state has been of interest in various research fields, not only in superconductors in solid state physics, but also in neutral Fermion superfluid of ultracold atomic gases and in color superconductivity in high energy physics. In spite of extensive studies of various superconductors, there has been no undisputed experimental verification of the FFLO state, mainly because of the very stringent conditions required of the superconducting materials. Among several classes of materials, certain heavy fermion and organic superconductors are believed to provide conditions that are favorable to the formation of the FFLO state. This review presents recent experimental and theoretical developments of the FFLO state mainly in heavy fermion superconductors. In particular we address the recently discovered quasi-two-dimensional superconductor CeCoIn5, which is a strong candidate for the formation of the FFLO state.

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Section: Possible Fflo State In Heavy Fermion Superconductorsmentioning

confidence: 99%

Fulde–Ferrell–Larkin–Ovchinnikov State in Heavy Fermion Superconductors

2007

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“…Recently, it has been sometimes suggested that organic, high-T c copper oxide and heavy fermion superconductors can be candidates of the FFLO superconductors, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] since they have large upper critical fields such that strong spin magnetism is attainable and also because they can be clean type-II superconductors.…”

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Structure of the Fulde-Ferrell-Larkin-Ovchinnikov State in Two-Dimensional Superconductors

1998

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Nonuniform superconducting state due to strong spin magnetism is studied in two-dimensional (2D) type-II superconductors near the second order phase transition line between the normal and superconducting states. The optimum spatial structure of the order parameter is examined in systems with cylindrically symmetric Fermi surfaces. It is found that states with 2D structures have lower free energies than the traditional one-dimensional solutions, at low temperatures and high magnetic fields. For s-wave pairing, triangular, square, and hexagonal states are favored depending on the temperature, while square states are favored at low temperatures for d-wave pairing. In these states, the order parameters have 2D structures such as square and triangular lattices.

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“…Such a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state has never been observed in conventional low-T c superconductors. Recently it has attracted renewed interest in the context of organic, heavy-fermion, and high-T c cuprate superconductors [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. These new classes of superconductors are believed to provide conditions that are favorable to the formation of FFLO state, because many of them are i) strongly type II superconductors so that the upper critical field H c2 can easily approach the Pauli paramagnetic limit; and (ii) layered compounds so that when a magnetic field is applied parallel to the conducting plane, the orbital effect is minimal, and the Zeeman effect (which is the driving force for the formation of FFLO state) dominates the physics.…”

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confidence: 99%

Josephson Effect in Fulde-Ferrell-Larkin-Ovchinnikov Superconductors

Yang

Agterberg

2000

Phys. Rev. Lett.

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Due to the difference in the momenta of the superconducting order parameters, the Josephson current in a Josephson junction between a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor and a conventional BCS superconductor is suppressed. We show that the Josephson current may be recovered by applying a magnetic field in the junction. The field strength and direction at which the supercurrent recovery occurs depend upon the momentum and structure of the order parameter in the FFLO state. Thus the Josephson effect provides an unambiguous way to detect the existence of an FFLO state, and to measure the momentum of the order parameter.It was suggested more than thirty years ago by Fulde and Ferrell [1], and Larkin and Ovchinnikov [2], that an inhomogeneous superconductor with an order parameter that oscillates spatially may be stabilized by a large external magnetic or internal exchange field. Such a FuldeFerrell-Larkin-Ovchinnikov (FFLO) state has never been observed in conventional low-T c superconductors. Recently it has attracted renewed interest in the context of organic, heavy-fermion, and high-T c cuprate superconductors [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. These new classes of superconductors are believed to provide conditions that are favorable to the formation of FFLO state, because many of them are i) strongly type II superconductors so that the upper critical field H c2 can easily approach the Pauli paramagnetic limit; and (ii) layered compounds so that when a magnetic field is applied parallel to the conducting plane, the orbital effect is minimal, and the Zeeman effect (which is the driving force for the formation of FFLO state) dominates the physics. Indeed, some experimental indications of the existence of the FFLO state have been reported [3,10,12,18].The main difficulty in the experimental search for the FFLO state is that just like the BCS state, the FFLO state is a superconducting state. The distinction between the two is a subtle difference in the structure of the superconducting order parameter, which is difficult to detect using ordinary experimental techniques. Previous experiments have focused on thermodynamic signatures of possible phase transitions from the BCS to FFLO state, which is believed to be first order (see, however, Ref. [6]). But such signatures can be caused by other phase transitions that have nothing to do with the superconducting order parameter. Thus it is very difficult to establish the presence of an FFLO state this way without any ambiguity.In this paper we propose using the Josephson effect to detect the existence of FFLO states. Our proposal has some similarity in spirit to the basic ideas behind the "phase sensitive" experiments [20] that established the predominant d-wave symmetry of the order parameter in cuprate superconductors. Specifically, we predict: (i) The Josephson current in a Josephson junction between a conventional BCS superconductor and an FFLO superconductor is suppressed, due to the difference in momenta of the order par...

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Fulde-Ferrell state in heavy-fermion superconductors

Cited by 34 publications

References 11 publications

Fulde–Ferrell–Larkin–Ovchinnikov State in Heavy Fermion Superconductors

Fulde–Ferrell–Larkin–Ovchinnikov State in Heavy Fermion Superconductors

Structure of the Fulde-Ferrell-Larkin-Ovchinnikov State in Two-Dimensional Superconductors

Josephson Effect in Fulde-Ferrell-Larkin-Ovchinnikov Superconductors

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