Nernst effect in the electron-doped cuprate superconductors

Hackl, Andreas; Sachdev, Subir

doi:10.1103/physrevb.79.235124

Cited by 28 publications

(34 citation statements)

References 38 publications

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“…almost coinciding with the strong drop in the electrical resistivity upon the onset of SDW order, a large negative contribution becomes apparent. The slope of ν(T ) changes strongly and the Nernst coefficient falls towards a large negative value of −2.5 µVK −1 T −1 at around 25 K. Qualitatively, this strong enhancement of the Nernst coefficient should be attributed to the Fermi surface reconstruction that is associated with the SDW phase [7,13]. The value of the Nernst coefficient in the SDW state is remarkably large, because it is about one order of magnitude larger than that generated by vortex flow in the superconducting samples (see below) or in, e.g., cuprate superconductors [5,18] which is often considered as a benchmark for a large Nernst effect.…”

Section: Nernst Effect and Sdw Fluctuations In The Iron-based Supercomentioning

confidence: 97%

“…The degree of its violation can be determined experimentally by comparing the measured ν with the term S tan θ /B, which can be calculated from electrical resistivity, thermopower, and Hall data. A little more than ten years ago, the Nernst effect of unconventional superconductors began to attract considerable attention [1,2,4,5,6,7,8,9,10,11,12,13,14]. One reason is that for type-II superconductors it is strongly enhanced by movement of magnetic flux lines (vortices) [15,16,17,18], where the Nernst coefficient ν is directly proportional to the drift velocity of the vortices, which has rendered this transport quantity a valuable tool for studying their dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…More specifically, it was proposed that in the pseudogap phase above T c long-range phase coherence of the superconducting order parameter is lost while the pair amplitude remains finite. One more recent proposal to explain an unusual Nernst response in the cuprates was that Fermi surface distortions due to stripe or spin density wave (SDW) order could lead to an enhanced Nernst effect [6,7,8,14]. In particular, for stripe ordering La 1.8−x Eu 0.2 Sr x CuO 4 and La 1.6−x Nd 0.4 Sr x CuO 4 , an enhanced positive Nernst signal at elevated temperature has been associated with a Fermi surface reconstruction due to stripe order [6].…”

Section: Introductionmentioning

confidence: 99%

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Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Heß

2012

NATO Science for Peace and Security Series B: Physics and Biophysics

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The Nernst effect has recently proven a sensitive probe for detecting unusual normal state properties of unconventional superconductors. In particular, it may sensitively detect Fermi surface reconstructions which are connected to a charge or spin density wave (SDW) ordered state, and even fluctuating forms of such a state. Here we summarize recent results for the Nernst effect of the iron pnictide superconductor LaO 1−x F x FeAs, whose ground state evolves upon doping from an itinerant SDW to a superconducting state, and the cuprate superconductor La 1.8−x Eu 0.2 Sr x CuO 4 which exhibits static stripe order as a ground state competing with the superconductivity. In LaFeAsO 1−x F x , the SDW order leads to a huge Nernst response, which allows to detect even fluctuating SDW precursors at superconducting doping levels where long range SDW order is suppressed. This is in contrast to the impact of stripe order on the normal state Nernst effect in La 1.8−x Eu 0.2 Sr x CuO 4 . Here, though signatures of the stripe order are detectable in the temperature dependence of the Nernst coefficient, its overall temperature dependence is very similar to that of La 2−x Sr x CuO 4 , where stripe order is absent. The anomalies which are induced by the stripe order are very subtle and the enhancement of the Nernst response due to static stripe order in La 1.8−x Eu 0.2 Sr x CuO 4 as compared to that of the pseudogap phase in La 2−x Sr x CuO 4 , if any, is very small.

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Section: Nernst Effect and Sdw Fluctuations In The Iron-based Supercomentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Heß

2012

NATO Science for Peace and Security Series B: Physics and Biophysics

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“…Recent thermoelectric and Nernst effect experiments [8] and theory [9,10] have also provided support for the Fermi surface transformations associated with the QCP at x = x m . Associated measurements of the anisotropy in the Nernst co-efficient [11] have been proposed to be explained by the influence of nematic order in the Fermi surface [12]; this nematic order can be regarded as a remnant of a fluctuating SDW state, as is suggested by neutron scattering observations [13].…”

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confidence: 99%

Quantum criticality and the phase diagram of the cuprates

Sachdev

2010

Physica C: Superconductivity and its Applications

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I discuss a proposed phase diagram of the cuprate superconductors as a function of temperature, carrier concentration, and a strong magnetic field perpendicular to the layers. I show how the phase diagram gives a unified interpretation of a number of recent experiments. Superconductivity, Tokyo, Sep 7-12, 2009 Keynote talk, 9th International Conference on Materials and Mechanisms of H c2Figure 1: Proposed phase diagram of the cuprates showing the interplay between superconductivity (SC), spin density wave (SDW) order, and Fermi surface configuration as a function of carrier density (x), temperature (T ), and magnetic field (H) perpendicular to the layers. Full lines are thermal or quantum phase transitions, dashed lines are crossovers, and dotted lines are guides to the eye. The phase transitions associated with valence bond solid (VBS) (or "charge") and nematic order are not shown. The superconducting regions are colored pink. We have assumed the absence of interlayer coupling, and so the SDW order is long-ranged only at T = 0: it is present in the regions labeled "SDW" and on the thick orange line for x < x s . In the blue normal regions, the 'pseudogap' is between T c and T * , the 'Strange Metal' has an in-plane resistivity which is measured to be linear in T , and the "Large Fermi surface" has a conventional T 2 resistivity.This brief note contains a summary of the key aspects of the proposed phase diagram of the cuprate superconductors shown in Fig. 1, and the central role played by ideas of quantum criticality. A more detailed discussion can be found in another recent review by the author [1], which also contains more complete citations to the literature. Here, I will focus on the central physical ideas and highlight support from recent experiments.The phase transitions and crossovers in Fig. 1 appear quite intricate. However, they can be understood simply by focusing first on the quantum critical point (QCP) at doping density, x = x m , temperature T = 0, magnetic field H = 0. As indicated in Fig. 1, this quantum critical point is pre-empted by the onset of superconductivity.The QCP at x = x m is a transition between two metallic (hence the subscript m) Fermi liquid phases. At x > x m we have the full symmetry of the square lattice, and a "large" Fermi surface metal consisting of a hole-like Fermi surface enclosing the area 1 + x expected from the Luttinger theorem (this is for hole doping; with electron doping, x, the area enclosed is 1 − x). At x < x m we have the onset of spin density wave (SDW) order, and this breaks apart the large Fermi surface into "small" Fermi pockets. Nevertheless the Luttinger theorem continues to be obeyed, after accounting for the large unit cell created by the SDW order. The ultimate theory of this quantum critical point is not fully understood, despite much theoretical attention [2].Strong evidence for the QCP at x = x m , and its associated T > 0 crossovers comes from recent experiments on Nd-LSCO [3,4]. They detected the crossover between "Strange Metal" and "Fl...

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“…Only recently, a second contribution to the Nernst signal has been identified and associated to quasiparticle physics. 16 Theoretically, the quasiparticle Nernst effect in the presence of antiferromagnetic 17 and stripe 18 order has been investigated.…”

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Nernst-effect anisotropy as a sensitive probe of Fermi-surface distortions from electron-nematic order

Hackl

Vojta

2009

Phys. Rev. B

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We analyze the thermoelectric response in layered metals with spontaneously broken rotation symmetry. We identify the anisotropy of the quasiparticle Nernst signal as an extremely sensitive probe of Fermi surface distortions characteristic of the ordered state. This is due to a subtle interplay of different transport anisotropies which become additionally enhanced near van-Hove singularities. Applied to recent experiments, our results reinforce the proposal that the underdoped cuprate superconductor YBa2Cu3O 6+δ displays such "electron-nematic" order in the pseudogap regime.Spontaneous breaking of lattice rotation symmetry due to electronic correlations is currently in the focus of intense interest, most prominently in cuprate hightemperature superconductors such as YBa 2 Cu 3 O 6+δ (Refs. 1-3) and in the metamagnetic metal Sr 3 Ru 2 O 7 (Ref. 4). In analogy to liquid crystals, a phase with broken rotation (but preserved translation) symmetry has been dubbed electron nematic. 5In cuprates, electron-nematic order has been discussed early on as intermediate phase which occurs upon melting of a uni-directional charge-density-wave ("stripe") phase. 5-7 Microscopically, it is one of the known instabilities of the two-dimensional (2d) Hubbard model. [8][9][10] The first clear-cut signature of electron-nematic order in cuprates was found in neutron scattering experiments on YBa 2 Cu 3 O 6.45 , 1 where the spin-fluctuation spectrum was found to develop a distinct anisotropic incommensurability below a temperature T of about 150 K. Earlier transport measurements on YBa 2 Cu 3 O 6+δ (Ref. 11) also detected resistivity anisotropies ρ a /ρ b of order 2 in the underdoped regime, but remained less conclusive. The reason is that the crystal structure of YBa 2 Cu 3 O 6+δ contains CuO chains which break the otherwise tetragonal symmetry of the CuO 2 planes. In an orderparameter language, this implies a small field which couples linearly to the nematic order parameter. This has two main effects: (i) potentially existing nematic order will be aligned and (ii) a nematic ordering transition will be smeared out. While (i) enables observables to show a macroscopic anisotropy, which might otherwise be masked by domain formation, (ii) implies that electronic nematic order and purely structural effects cannot be sharply distinguished. Remarkably, locally broken rotation symmetry has been found on the surface of Bi 2 Sr 2 CaCu 2 O 8+δ and Ca 2−x Na x CuO 2 Cl 2 using scanning tunneling microscopy. 12 In Sr 3 Ru 2 O 7 , nematic order is a candidate explanation for the low-T phase which masks the metamagnetic critical endpoint at around 8 T. 4,13 Resistivity anisotropies have been detected here, but a full picture has not yet emerged, because the rather unusual thermodynamics near the low-T phase boundaries is not understood.Very recent measurements 2,3 of the Nernst effect, 14 that is the transverse voltage induced by a thermal gradient in the presence of a magnetic field, have uncovered a surprisingly large anisotropy in YBa 2 Cu 3 O 6+δ ...

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Nernst effect in the electron-doped cuprate superconductors

Cited by 28 publications

References 38 publications

Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Quantum criticality and the phase diagram of the cuprates

Nernst-effect anisotropy as a sensitive probe of Fermi-surface distortions from electron-nematic order

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