Unconventional Low-Energy Excitations of Cuprate Superconductors

Yeh, N.-C.; Beyer, André

doi:10.1142/s021797920905403x

Cited by 14 publications

(59 citation statements)

References 175 publications

(480 reference statements)

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“…In this case, the term in the Landau free energy ρ Q α Δ Q α Δ Ã d implies that CDWs with wave vectors Q α are predicted to appear in the superconducting state. It is intriguing that STM measurements at 6 K on optimally doped YBCO have found charge ordering with two sets of ordering vectors at δ ¼ 0.28 AE0.03 and 0.14 AE0.01 (in units of 2π) along the x and y axes [49]. It is tempting to reinterpret these CDWs to correspond to our ρ 2Q α and ρ Q α , respectively.…”

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confidence: 97%

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

2014

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The enigmatic pseudogap phase in underdoped cuprate high-T c superconductors has long been recognized as a central puzzle of the T c problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing.Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing. DOI: 10.1103/PhysRevX.4.031017 Subject Areas: Condensed Matter Physics, SuperconductivitySince the early days of cuprate superconductivity research, the pseudogap phase has been identified as a central piece of the high-T c puzzle [1]. The pseudogap opens below a temperature T Ã much above T c in underdoped cuprates, and it is visible in the spin susceptibility as detected by the Knight shift, in tunneling spectroscopy and in c-axis conductivity. Angle-resolved photoemission (ARPES) shows that the pseudogap opens in the antinodal region near ð0; πÞ (we set the lattice constant a to unity), leaving behind ungapped "Fermi arcs" centered around the nodes. Recent x-ray scattering data [2][3][4][5] reveal that the pseudogap is likely to be a distinct phase, characterized by the onset of a charge density wave (CDW) with wave vectors at ð0; AEδÞ and ðAEδ; 0Þ, where δ decreases with increasing doping, thus confirming evidence for charge order found earlier by scanning tunneling microscope (STM) [6][7][8][9] and nuclear magnetic resonance (NMR) experiments [10]. Recent advances include STM and x-ray studies on the same Bi 2 Sr 2 CaCu 2 O 8þx (Bi-2212) samples [11]. Other signatures include Kerr rotation [12], the emergence of anisotropy in the Nernst effect, etc. [13]. (Another set of exp...

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confidence: 97%

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

2014

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“…The histogram of the spectral evolution from  SC to  CO and another sub-gap feature at with increasing H is shown in Fig. 2e, which is in stark contrast to the vortex-state spectral evolution of conventional type-II superconductors [4].…”

Section: Vortex-state Ldos Of Hole-type Cupratesmentioning

confidence: 82%

“…In addition to microscopic STS studies, the effects of Ca-doping on macroscopic vortex dynamics were investigated by measuring the irreversibility temperature T irr (H,x,p) from the zerofield-cool (ZFC) and field-cool (FC) magnetization (M) vs. temperature (T) curves [21]. samples [4][5][6][7], which differ from the strong spatially inhomogeneous tunneling spectra observed in Bi-2212 [17,18]. In contrast, for Ca-doped Y-123, the zerofield LDOS spectra revealed spatial homogeneity only within a limited range (up to ~ 10 2 nm in length); variations in the spectral characteristics appeared over a long range, which may be attributed to disorder in Ca-doping.…”

Section: Methodsmentioning

confidence: 99%

“…The low-energy quasiparticle excitations of cuprate superconductors exhibit various spectral characteristics that differ from those of simple Bogoliubov quasiparticles for pure superconductors because of the presence of competing orders (COs) in the ground state of under-and optimally doped cuprates [1][2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Some of the best known unconventional spectral characteristics include: the presence (absence) of pseudogap and Fermi arc phenomena in hole-type (electrontype) cuprates [4][5][6][7][8][9][10][11][12]; dichotomy of the quasiparticle coherence for momentum near the nodal and anti-nodal parts of the Fermi surface [9,12,13]; pseudogap (PG)-like spectral features inside vortex cores [4][5][6][7]; and non-universal spectral homogeneity among different types of cuprates [4,5,[14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Scanning Tunneling Spectroscopic Studies of the Low-Energy Quasiparticle Excitations in Cuprate Superconductors

Yeh

Teague

et al. 2012

J Supercond Nov Magn

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We report scanning tunneling spectroscopic (STS) studies of the low-energy quasiparticle excitations of cuprate superconductors as a function of magnetic field and doping level. Our studies suggest that the origin of the pseudogap (PG) is associated with competing orders (COs), and that the occurrence (absence) of PG above the superconducting (SC) transition T c is associated with a CO energy  CO larger (smaller) than the SC gap  SC . Moreover, the spatial homogeneity of  SC and  CO depends on the type of disorder in different cuprates: For optimally and under-doped YBa 2 Cu 3 O 7 (Y-123), we find that  SC <  CO and that both  SC and  CO exhibit long-range spatial homogeneity, in contrast to the highly inhomogeneous STS in Bi 2 Sr 2 CaCu 2 O 8+x (Bi-2212). We attribute this contrast to the stoichiometric cations and ordered apical oxygen in Y-123, which differs from the non-stoichiometric Bi-to-Sr ratio in Bi-2212 with disordered Sr and apical oxygen in the SrO planes. For Ca-doped Y-123, the substitution of Y by Ca contributes to excess holes and disorder in the CuO 2 planes, giving rise to increasing inhomogeneity, decreasing  SC and  CO , and a suppressed vortex-solid phase. For electron-type cuprate Sr 0.9 La 0.1 CuO 2 (La-112), the homogeneous  SC and  CO distributions may be attributed to stoichiometric cations and the absence of apical oxygen, with  CO <  SC revealed only inside the vortex cores. Finally, the vortex core radius ( halo ) in electron-type cuprates is comparable to the SC coherence length  SC , whereas  halo ~ 10 SC in hole-type cuprates, suggesting that  halo may be correlated with the CO strength.The vortex-state irreversibility line in the magnetic field versus temperature phase diagram also reveals doping dependence, indicating the relevance of competing orders to vortex pinning.

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Mean-field approach to unconventional superconductivity

Mauger¹,

Noat²

2014

Physica C: Superconductivity and its Applications

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Unconventional Low-Energy Excitations of Cuprate Superconductors

Cited by 14 publications

References 175 publications

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

Scanning Tunneling Spectroscopic Studies of the Low-Energy Quasiparticle Excitations in Cuprate Superconductors

Mean-field approach to unconventional superconductivity

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