Heavy-Fermion Superconductivity

Riseborough, Peter S.; Schmiedeshoff, G. M.; Smith, James L.

doi:10.1007/978-3-540-73253-2_19

Cited by 5 publications

(5 citation statements)

References 499 publications

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“…A number of Uranium-based heavy fermion compounds show strong evidence of unconventional triplet pairing states with nontrivial topological properties [175][176][177][178]. Among them, UPt 3 is probably the most promising candidate for spin-triplet superconductivity, and has received much attention [171].…”

Section: Nodal Superconductors With Spin-triplet Pairingmentioning

confidence: 99%

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Topological surface states in nodal superconductors

Schnyder

Brydon

2015

J. Phys.: Condens. Matter

159

190

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In this work, we show that a giant spin current can be injected into a nodal topological supercon-ductor, using a normal paramagnetic lead, through a large number of zero energy Majorana fermions at the superconductor edge. The giant spin current is caused by the selective equal spin Andreev reflections (SESAR) induced by Majorana fermions. In each SESAR event, a pair of electrons with certain spin polarization are injected into the nodal topological superconductor, even though the pairing in the bulk of the nodal superconductor is spin-singlet s-wave. We further explain the origin of the spin current by showing that the pairing correlation at the edge of a nodal topological superconductor is predominantly equal spin-triplet at zero energy. The experimental consequences of SESAR in nodal topological superconductors are discussed. Introduction-The search for Majorana fermions in condensed matter systems has been an important topic in recent years [1-5]. This search is strongly motivated by the fact that Majorana fermions are non-Abelian particles and have potential applications in quantum computation [6-8]. Recently, it was further pointed out that Majorana fermions, due to their self-Hermitian properties , could induce spin currents in paramagnetic leads [9-11] and correlated spin currents in spatially separated leads [12, 13]. These properties make it possible for Ma-jorana fermions to have potential applications in super-conducting spintronics [14, 15]. In particular, it was pointed out that a single Majo-rana end state of a topological superconducting wire can induce the so-called selective equal spin Andreev reflection (SESAR) at the normal lead/topological supercon-ductor (N/TS) interface [9]. In SESAR processes, only electrons with certain spin polarization n in the normal lead can couple to the Majorana fermion and undergo Andreev reflections. Importantly, the reflected holes are due to missing electrons with the same spin polarization n below the Fermi energy. As a result, two electrons with equal spin tunnel into the superconducting wire and form a spin-triplet Cooper pair in each Andreev reflection event. On the other hand, electrons with opposite spin polarization −n in the normal lead are decoupled from the Majorana fermion and get reflected as electrons with unchanged spin. Therefore, a spin current with spin polarization in the n direction can be injected into the superconductor using a paramagnetic lead. At the same time, a spin current is generated in the lead. In this work, instead of studying isolated Majorana modes, we study the spin transport properties of the 2D nodal topological superconductor with a large number of spatially overlapping zero energy Majorana modes at the sample edge [16-19]. The zero energy edge modes are associated with Majorana flat band (MFB), which connects the nodal points of the superconductor in the projected band structure. These flat bands are analogous to the surface Fermi arcs connecting the Weyl points in Weyl semimetals [20, 21]. Specifically, we consider a 2D ...

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Section: Nodal Superconductors With Spin-triplet Pairingmentioning

confidence: 99%

“…In all these materials superconductivity appears close to an antiferromagnetic quantum critical point and is believed to be mediated by spin fluctuations [142,177,178]. In contrast to the ferromagnetic superconductors, however, magnetic order in the Cerium compounds competes with superconductivity.…”

Section: Nodal Superconductors With Spin-singlet Pairingmentioning

confidence: 99%

Topological surface states in nodal superconductors

Schnyder

Brydon

2015

J. Phys.: Condens. Matter

159

190

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“…They have a specific heat below T c which is well-approximated with a power law behaviour (see e.g. [19]), heavy fermions at T < T c : where n ∼ 2 − 3, and γ 0 and κ are constants. In other words, due to the unusual properties of the gap, the specific heat is no longer exponentially suppressed when T < T c .…”

Section: Comments On Connections With Real-world Superconductorsmentioning

confidence: 99%

Exploring colourful holographic superconductors

Peeters

Powell

Zamaklar

2009

J. High Energy Phys.

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We explore a class of holographic superconductors built using non-abelian condensates on probe branes in conformal and non-conformal backgrounds. These are shown to exhibit behaviour of the specific heat which resembles that of heavy fermion compounds in the superconducting phase. Instead of showing BCS-like exponential behaviour, the specific heat is polynomial in the temperature. It exhibits a jump at the critical temperature, in agreement with real-world superconductors. We also analyse the behaviour of the energy gap and the AC and DC conductivities, and find that the systems can be either semi-conducting or metallic just above the critical temperature.

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“…The consideration of quantum criticality leads to new physics (non-Fermi liquid behavior ), for both models. Also, the particular questions of the pseudogap appearance [94] in high-T c systems and, e.g., the hidden-order existence in URu 2 Si 2 [95], are not tackled here. Nonetheless, I firmly believe that the considerations touched upon here provide a first if not substantial step in understanding theoretically the superconductivity in the strong-correlation limit for the narrow-band fermions.…”

Section: Discussionmentioning

confidence: 99%

Fifty years of Hubbard and Anderson lattice models: from magnetism to unconventional superconductivity - A brief overview

Spałek

2014

Philosophical Magazine

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We briefly overview the importance of Hubbard and Anderson-lattice models as applied to explanation of high-temperature and heavy-fermion superconductivity. Application of the models during the last two decades provided an explanation of the paired states in correlated fermion systems and thus extended essentially their earlier usage to the description of itinerant magnetism, fluctuating valence, and the metal-insulator transition. In second part, we also present some of the new results concerning the unconventional superconductivity and obtained very recently in our group. A comparison with experiment is also discussed, but the main emphasis is put on rationalization of the superconducting properties of those materials within the real-space pairing mechanism based on either kinetic exchange and/or Kondo-type interaction combined with the electron correlation effects.

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Heavy-Fermion Superconductivity

Cited by 5 publications

References 499 publications

Topological surface states in nodal superconductors

Topological surface states in nodal superconductors

Exploring colourful holographic superconductors

Fifty years of Hubbard and Anderson lattice models: from magnetism to unconventional superconductivity - A brief overview

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