Interior gap superconductivity in heavy fermions

Continentino, M. A.; Tavares, Igor

doi:10.1016/j.physb.2007.10.313

Cited by 4 publications

(24 citation statements)

References 4 publications

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“…In the normal phase and in the absence of the fictitious field, the relevant zero order Green's functions can be easily calculated [11]. They are given by,…”

Section: The Modelmentioning

confidence: 99%

“…[12]. For intra-band interactions, the instability is towards a homogeneous superconducting phase when the condition 1 − U χ aa 0 (q = 0, ω 0 = 0) = 0 is fulfilled [11].…”

Section: The Modelmentioning

confidence: 99%

“…Recently, we proposed a new mechanism for destroying superconductivity which is specific for multi-band materials as heavy fermions [1,11]. It occurs because the narrow band of quasi-particles which form the Cooper pairs is hybridized with a band of normal electrons.…”

Section: Introductionmentioning

confidence: 99%

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Fluctuations in a superconducting quantum critical point of multi-band metals

Ramires¹,

Continentino²

2011

J. Phys.: Condens. Matter

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In multi-band metals quasi-particles arising from different atomic orbitals coexist at a common Fermi surface. Superconductivity in these materials may appear due to interactions within a band (intra-band) or among the distinct metallic bands (inter-band). Here we consider the suppression of superconductivity in the intra-band case due to hybridization. The fluctuations at the superconducting quantum critical point (SQCP) are obtained calculating the response of the system to a fictitious space and time dependent field, which couples to the superconducting order parameter. The appearance of superconductivity is related to the divergence of a generalized susceptibility. For a single band superconductor this coincides with the Thouless criterion. For fixed chemical potential and large hybridization, the superconducting state has many features in common with breached pair superconductivity with unpaired electrons at the Fermi surface. The T=0 phase transition from the superconductor to the normal state is in the universality class of the density-driven Bose-Einstein condensation. For fixed number of particles and in the strong coupling limit, the system still has an instability to the normal sate with increasing hybridization.

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“…In the normal phase and in the absence of the fictitious field, the relevant zero order Green's functions can be easily calculated [11]. They are given by,…”

Section: The Modelmentioning

confidence: 99%

“…[12]. For intra-band interactions, the instability is towards a homogeneous superconducting phase when the condition 1 − U χ aa 0 (q = 0, ω 0 = 0) = 0 is fulfilled [11].…”

Section: The Modelmentioning

confidence: 99%

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Fluctuations in a superconducting quantum critical point of multi-band metals

Ramires¹,

Continentino²

2011

J. Phys.: Condens. Matter

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“…The Fermi wave-vector mismatch δk F in this case is controlled by varying the density of the atoms and this allows the phase diagram to be fully explored. In the core of neutron stars, up an down quarks, in different numbers, with attractive interactions may give rise to color inter-band superconductivity 13,14 . We neglect here orbital effects.…”

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confidence: 99%

“…13 an FFLO phase can also be induced by hybridization (V ). The results above can be easily extended for the case of hybrid bands 13 . The Fermi wave-vectors mismatch is given by, k a F − k b F = 4V /v F (1 + α), where α < 1 is the ratio of the effective masses of the quasi-particles.…”

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confidence: 99%

Quantum criticality in inter-band superconductors

Ramires¹,

Continentino²

2010

J. Phys.: Condens. Matter

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In fermionic systems with different types of quasi-particles, attractive interactions can give rise to exotic superconducting states, as pair density wave (PDW) superconductivity and breached pairing. In the last years the search for these new types of ground states in cold atom and in metallic systems has been intense. In the case of metals the different quasi-particles may be the up and down spin bands in an external magnetic field or bands arising from distinct atomic orbitals that coexist at a common Fermi surface. These systems present a complex phase diagram as a function of the difference between the Fermi wave-vectors of the different bands. This can be controlled by external means, varying the density in the two-component cold atom system or, in a metal, by applying an external magnetic field or pressure. Here we study the zero temperature instability of the normal system as the Fermi wave-vectors mismatch of the quasi-particles (bands) is reduced and find a second order quantum phase transition to a PDW superconducting state. From the nature of the quantum critical fluctuations close to the superconducting quantum critical point (SQCP), we obtain its dynamic critical exponent. It turns out to be z = 2 and this allows to fully characterize the SQCP for dimensions d ≥ 2.In strongly correlated materials superconductivity can be suppressed in different ways. Most commonly, this is accomplished by an external magnetic field, applied pressure or doping 1-7 . However, the point in the phase diagram where the critical temperature T c vanishes as a function of the external parameters is not necessarily associated with a SQCP. In the case of superconductivity induced by antiferromagnetic fluctuations due to the proximity of an antiferromagnetic quantum critical point (AFQCP) 8 , as the system moves away from the AFQCP, these fluctuations change from attractive to repulsive and superconductivity just fades away 9 .Inter-band superconductivity is a long standing problem in condensed matter physics 10,11 . It can be realized, for example, by applying an external magnetic field in a metallic system. The field splits the band and the phase diagram as a function of the mismatch of the Fermi wave-vectors of the up and down spin bands can be investigated. It also occurs for the case of superconductivity mediated by valence fluctuations, where the most relevant correlations are due to inter-band pairing 12 . In multi-band metals, pressure can be used to change the hybridization and the mismatch of the Fermi wavevectors of the different bands coexisting at the common Fermi surface 13 . More recently this problem has received much attention due to the possibility of investigating it in cold atom systems. In this case the attractive interaction between two fermionic systems with different Fermi wave-vectors can be tuned by Feshbach resonance 14 . The Fermi wave-vector mismatch δk F in this case is controlled by varying the density of the atoms and this allows the phase diagram to be fully explored. In the core of neutron st...

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