Spectral signatures of modulated<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi></mml:math>-wave superconducting phases

Baruch, Shirit; Orgad, Dror

doi:10.1103/physrevb.77.174502

Cited by 71 publications

(97 citation statements)

References 45 publications

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“…The gap function expected for a PDW state has been calculated by Baruch and Orgad [157]. They find that the gap should be large in the antinodal regions, but that there should be a gapless nodal arc.…”

Section: Arpes Studiesmentioning

confidence: 99%

Spins, stripes, and superconductivity in hole-doped cuprates

Tranquada¹

2013

AIP Conference Proceedings

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Abstract. One of the major themes in correlated electron physics over the last quarter century has been the problem of high-temperature superconductivity in hole-doped copper-oxide compounds. Fundamental to this problem is the competition between antiferromagnetic spin correlations, a symptom of strong Coulomb interactions, and the kinetic energy of the doped carriers, which favors delocalization. After discussing some of the early challenges in the field, I describe the experimental picture provided by a variety of spectroscopic and transport techniques. Then I turn to the technique of neutron scattering, and discuss how it is used to determine spin correlations, especially in model systems of quantum magnetism. Neutron scattering and complementary techniques have determined the extent to which antiferromagnetic spin correlations survive in the cuprate superconductors. One experimental case involves the ordering of spin and charge stripes. I first consider related measurements on model compounds, such as La 2−x Sr x NiO 4+δ , and then discuss the case of La 2−x Ba x CuO 4 . In the latter system, recent transport studies have demonstrated that quasi-two-dimensional superconductivity coexists with the stripe order, but with frustrated phase order between the layers. This has led to new concepts for the coexistence of spin order and superconductivity. While the relevance of stripe correlations to high-temperature superconductivity remains a subject of controversy, there is no question that stripes are an intriguing example of electron matter that results from strong correlations.Keywords: superconductivity, antiferromagnetism, charge order, stripes, cuprates, nickelates, neutron scattering PACS: 78.70.Nx OPENING REMARKSCuprate superconductivity is a fascinating field, with an enormous literature. There have been a great many measurements done on a wide variety of cuprate families. There are numerous theoretical perspectives on the nature of these materials and on the mechanism of superconductivity.I approach this topic not as an unbiased outside observer, but as a participant who has been around from the beginning. My purpose here is not to present a balanced review of all work and perspectives in the field, as there would be too much to cover. Instead, I will present one story about hole-doped cuprates, based largely on experiment and especially on neutron scattering studies. Since one of the main advantages of neutrons is their ability to follow dynamic antiferromagnetic spin correlations, it should come as no surprise that they will play a key role in the story.I have tried to cite sufficient references (especially review articles) so that the curious reader can find further information and potentially a starting point in searching the broader literature. I have not attempted to cite all relevant work, as that would have been

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Section: Arpes Studiesmentioning

confidence: 99%

Spins, stripes, and superconductivity in hole-doped cuprates

Tranquada¹

2013

AIP Conference Proceedings

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“…Specifically, so long as the order parameter is not too large, an ungapped reconstructed Fermi surface remains 18,19 . Thus, a PDW typically has a finite density of states in the superconducting phase.…”

Section: E Quasiparticle Spectrum Of a Striped Superconductormentioning

confidence: 99%

Theory of the striped superconductor

2009

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We define a distinct phase of matter, a pair density wave (PDW), in which the superconducting order parameter, φ( r, r ′ ), varies periodically as a function of position such that when averaged over the center of mass position, ( r + r ′ )/2, all components of φ vanish identically. Specifically, we study the simplest, unidirectional PDW, the "striped superconductor," which we argue may be at the heart of a number of spectacular experimental anomalies that have been observed in the failed high temperature superconductor, La2−xBaxCuO4. We present a solvable microscopic model with strong electron-electron interactions which supports a PDW groundstate. We also discuss, at the level of Landau theory, the nature of the coupling between the PDW and other order parameters, and the origins and some consequences of the unusual sensitivity of this state to quenched disorder. I. A NEW PHASE OF MATTERSuperconductivity which arises from the pairing of electrons in time reversed states is well understood as a weak coupling "Fermi surface" instability -a consequence of arbitrarily weak effective attractive interactions. 1 In this paper we explore a new type of superconducting state, a "pair density wave" (PDW), which is a distinct state of matter, and which does not occur under generic circumstances in the weak coupling limit -it requires interactions in excess of a critical strength. The PDW spontaneously breaks the global gauge symmetry, in precisely the same way as a conventional superconductor does. Thus, the order parameter is a charge 2e complex scalar field, φ. However, it also spontaneously breaks some of the translational and point group symmetries of the host crystal, in the same way as a conventional charge-density wave (CDW). In a PDW, for fixed r − r ′ , the order parameteris a periodic function of the center of mass coordinate, R ≡ ( r + r ′ )/2. Here, ψ † σ ( r) is the electron creation operator at position r with spin polarization σ. We will focus on the case in which translational symmetry is broken only in one direction, i.e. a unidirectional PDW or equivalently a "striped superconductor."Accompanying the PDW there is, as we will show below, induced CDW order with half the period of the PDW. However, the PDW differs from a state of coexisting superconducting and CDW order 2 , which has also been previously called a "pair-density wave". 3 Unlike the pair-density-wave state of Ref.[2], the average value of the superconducting order parameter vanishes for the PDW state we discuss here. This is a defining symmetry property of this state. The PDW is more closely analogous to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state 5 which arises, under appropriate circumstances, when the electron gas is partially polarized by an applied magnetic field. However, explicit time-reversal symmetry breaking is an essential ingredient of the FFLO state, and is responsible for lifting the degeneracy ("nesting") between time-reversed pairs of quasiparticle states. In the absence of quenched disorder, the PDW state preserves time-r...

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“…In analogy with superconductors, the spinons can condense in pairs or clusters, breaking the U (1) gauge symmetry to a discrete subgroup and gapping the gauge-field fluctuations via the Anderson-Higgs mechanism. Recently, it has been recognized [29,32] that exotic superconducting states can exist with appropriate broken symmetries which support a Fermi surface of Bogoliubov quasi-particles, while still exhibiting the standard Meissner effect; the spin-liquid analogue of these states have a gap to all gauge-field fluctuations in the presence of a robust spinon Fermi surface, and are therefore promising candidates to explain the dmit phenomenology.…”

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confidence: 99%

“…A specific version of this was proposed in [21]. The essential feature [32] of this state which prevents it from fully gapping the spinon-Fermi surface is that the gap parameter changes sign, ∆(r) = −∆(r + eλ/2) under translation by 1/2 the PDW period, λ, so that the spatial averaged gap vanishes. (Q = (2π/λ)ê is the PDW ordering vector.)…”

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confidence: 99%

Gapless spin liquids: Stability and possible experimental relevance

2013

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For certain crystalline systems, most notably the organic compound EtMe3Sb[Pd(dmit)2]2, experimental evidence has accumulated of an insulating state with a high density of gapless neutral excitations that produce Fermi-liquid-like power laws in thermodynamic quantities and thermal transport. This has been taken as evidence of a fractionalized spin liquid state. In this paper, we argue that if the experiments are taken at face value, the most promising spin liquid candidates are a Z4 spin liquid with a pseudo-Fermi surface and no broken symmetries, or a Z2 spin-liquid with a pseudo-Fermi surface and at least one of the following spontaneously broken: (a) time-reversal and inversion, (b) translation, or (c) certain point-group symmetries. We present a solvable model on the triangular lattice with an (a) type Z2 spin liquid groundstate.

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Spectral signatures of modulatedd-wave superconducting phases

Cited by 71 publications

References 45 publications

Spins, stripes, and superconductivity in hole-doped cuprates

Spins, stripes, and superconductivity in hole-doped cuprates

Theory of the striped superconductor

Gapless spin liquids: Stability and possible experimental relevance

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