Frequency- and temperature-dependent conductivity in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml

Orenstein, J.; Thomas, G. A.; Millis, Andrew J.; Cooper, S. L.; Rapkine, D. H.; Timusk, T.; Schneemeyer, Lynn; Waszczak, J. V.

doi:10.1103/physrevb.42.6342

Cited by 400 publications

(221 citation statements)

References 69 publications

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“…This "Plankian" timescale has previously been proposed to underpin transport across many families of unconventional metals (refs. 15-17 and references therein) and is widely observed in optical data on cuprates (18)(19)(20)(21). A simple model based on the above ansatz shows excellent fit to the temperature dependence of the measured thermal diffusivity using measured material parameters.…”

Section: Significancementioning

confidence: 99%

Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x

Zhang

Levenson-Falk

Ramshaw

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The thermal diffusivity in the ab plane of underdoped YBCO crystals is measured by means of a local optical technique in the temperature range of 25-300 K. The phase delay between a point heat source and a set of detection points around it allows for high-resolution measurement of the thermal diffusivity and its in-plane anisotropy. Although the magnitude of the diffusivity may suggest that it originates from phonons, its anisotropy is comparable with reported values of the electrical resistivity anisotropy. Furthermore, the anisotropy drops sharply below the charge order transition, again similar to the electrical resistivity anisotropy. Both of these observations suggest that the thermal diffusivity has pronounced electronic as well as phononic character. At the same time, the small electrical and thermal conductivities at high temperatures imply that neither well-defined electron nor phonon quasiparticles are present in this material. We interpret our results through a strongly interacting incoherent electron-phonon "soup" picture characterized by a diffusion constant D ∼ v 2 B τ , where v B is the soup velocity, and scattering of both electrons and phonons saturates a quantum thermal relaxation time τ ∼ /k B T.thermal diffusivity | bad metals | electron-phonon T he standard paradigm for transport in metals relies on the existence of quasiparticles. Electronic quasiparticles conduct electricity and heat. Phonon quasiparticles, the collective excitations of the elastic solid (here, we discuss acoustic phonons) also conduct heat. Transport coefficients, such as electrical and thermal conductivities, can then be calculated using, for example, Boltzmann equations (1). However, such an approach fails when the quasiparticle mean free paths become comparable with the quasiparticle wavelength. For electrons, it is the Fermi wavelength (2-4), whereas for phonons, it is the larger of the interatomic distance or minimum excited phonon wavelength (5, 6). Understanding transport in nonquasiparticle regimes requires a new framework and has become a subject of intense theoretical effort in recent years, triggering an urgent need for experimental results that can shed light on such regimes. In particular, in ref. 7, the diffusivity was singled out as a key observable for incoherent nonquasiparticle transport, possibly subject to fundamental quantum mechanical bounds.In this work, we report high-resolution measurements of the thermal diffusivity of single-crystal underdoped YBCO6.60 (an ortho-II YBa2Cu3O6.60) and YBCO6.75 (an ortho-III YBa2Cu3O6.75). We are particularly interested in the anisotropy of the thermal diffusivity as measured along the principal axes a and b (which is the chain direction) in the temperature range 25-300 K. We use a noncontact optical microscope (see Fig. S1) to perform local thermal transport measurements on the scale of ∼10 µm, hence avoiding inhomogeneities, particularly twinning and grain boundary effects. Our principal experimental results are as follows. (i) The measured thermal diffusivity is...

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Section: Significancementioning

confidence: 99%

Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x

Zhang

Levenson-Falk

Ramshaw

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…This was motivated by the need to reconcile transport experiments [13][14][15][16] and photoemission data [17][18][19] in the underdoped region of cuprate superconductors: while photoemission data show Fermi arcs enclosing an area 1 + p (with p being the doping), transport measurements indicate plain Fermi-liquid properties consistent with an area p. In order to resolve this issue and produce a Fermi liquid which encloses an area p, the authors of Refs. [10][11][12] introduced a model for the pseudogap region of the cuprate superconductors which consists of two types of dimers: one spinless bosonic dimer -representing a valence bond between two neighboring spins -and one spin 1/2 fermionic dimer representing a hole delocalized between two sites.…”

Section: Introductionmentioning

confidence: 99%

d-wave superconductivity in boson+fermion dimer models

2017

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We present a slave-particle mean-field study of the mixed boson+fermion quantum dimer model introduced by Punk, Allais, and Sachdev [PNAS 112, 9552 (2015)] to describe the physics of the pseudogap phase in cuprate superconductors. Our analysis naturally leads to four charge e fermion pockets whose total area is equal to the hole doping p, for a range of parameters consistent with the t − J model for high temperature superconductivity. Here we find that the dimers are unstable to d-wave superconductivity at low temperatures. The region of the phase diagram with d-wave rather than s-wave superconductivity matches well with the appearance of the four fermion pockets. In the superconducting regime, the dispersion contains eight Dirac cones along the diagonals of the Brillouin zone.

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“…In normal metals, resistivity ρ saturates in the vicinity of Ioffe-Regel-Mott limit ρ IRM where elastic mean free path l min becomes comparable to interatomic distance [18,19]. In cuprates, however, signs of saturation are seen at ρ sat much larger than ρ IRM calculated from the semiclassical Boltzmann theory [20][21][22][23]. Moreover, ρ(1000 K) (∼ ρ sat ) in LSCO changes as 1/x, while for n ∝ x (Ref.…”

mentioning

confidence: 99%

Saturation of resistivity and Kohler's rule in Ni-dopedLa1.85Sr0.15CuO4cuprate

2017

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We present the results of electrical transport measurements of La1.85Sr0.15Cu1−yNiyO4 thin singlecrystal films at magnetic fields up to 9 T. Adding Ni impurity with strong Coulomb scattering potential to slightly underdoped cuprate makes the signs of resistivity saturation at ρsat visible in the measurement temperature window up to 350 K. Employing the parallel-resistor formalism reveals that ρsat is consistent with classical Ioffe-Regel-Mott limit and changes with carrier concentration n as ρsat ∝ 1/ √ n. Thermopower measurements show that Ni tends to localize mobile carriers, decreasing their effective concentration as n ∼ = 0.15 − y. The classical unmodified Kohler's rule is fulfilled for magnetoresistance in the nonsuperconducting part of the phase diagram when applied to the ideal branch in the parallel-resistor model.

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Frequency- and temperature-dependent conductivity inYBa2Cu3

Cited by 400 publications

References 69 publications

Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x

Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x

d-wave superconductivity in boson+fermion dimer models

Saturation of resistivity and Kohler's rule in Ni-dopedLa1.85Sr0.15CuO4cuprate

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Frequency- and temperature-dependent conductivity inYBa2Cu3

Cited by 400 publications

References 69 publications

Anomalous thermal diffusivity in underdoped YBa 2 Cu 3 O 6+x

Anomalous thermal diffusivity in underdoped YBa 2 Cu 3 O 6+x

d-wave superconductivity in boson+fermion dimer models

Saturation of resistivity and Kohler's rule in Ni-dopedLa1.85Sr0.15CuO4cuprate

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Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x

Anomalous thermal diffusivity in underdoped YBa ₂ Cu ₃ O _6+x