The electronic specific heat of cuprate superconductors

Loram, J. W.; Mirza, K. A.; Wade, J.M.; Cooper, J. R.; Liang, W. Y.

doi:10.1016/0921-4534(94)91331-5

Cited by 315 publications

(254 citation statements)

References 8 publications

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“…[30] interpreted this in terms of pair-breaking scattering. Co-existence of superconducting and normal charges at T → 0 in Tl2201 also shows up in specific heat measurements by Loram et al [74] shown in Fig. 7(a).…”

Section: Phase Separation In the Overdoped Regionmentioning

confidence: 85%

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Uemura¹

2004

J. Phys.: Condens. Matter

102

123

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To find out a primary determing factor of Tc and a pairing mechanism in high-Tc cuprates, we combine the muon spin relaxation results on ns/m * (superconducting carrier density / effective mass), accumulated over the last 15 years, with the results from neutron and Raman scattering, STM, specific heat, Nernst effect and ARPES measurements. We identify the neutron magnetic resonance mode as an analogue of roton minimum in the superfluid 4 He, and argue that ns/m * and the resonance mode energy ωres play a primary role in determining Tc in the underdoped region. We propose a picture that roton-like excitations in the cuprates appear as a coupled mode, which has the resonance mode for spin and charge responses at different momentum transfers but the same energy transfers, as detected respectively, by the neutron S=1 mode and the Raman S=0 A1g mode. We shall call this as the "hybrid spin/charge roton". After discussing the role of dimensionality in condensation, we propose a generic phase diagram of the cuprates with spatial phase separation in the overdoped region as a special case of the BE-BCS crossover conjecture where the superconducting coupling is lost rapidly in the overdoped region. Using a microscopic model of charge motion resonating with antiferomagnetic spin fluctuations, we propose a possibility that the hybrid spin/charge roton and higher-energy spin fluctuations mediate the superconducting pairing. In this model, the resonance modes can be viewed as a meson-analogue and the "dome" shape of the phase diagram can be understood as a natural consequence of departure from the competing Mott insulator ground state via carrier doping.

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Section: Phase Separation In the Overdoped Regionmentioning

confidence: 85%

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Uemura¹

2004

J. Phys.: Condens. Matter

102

123

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“…First, the pseudogap was found in the magnetic excitation channel by the nuclear magnetic resonance (NMR) experiment. 1) At present, the pseudogap phenomena have been observed in various quantities which include NMR, 1, 2, 3, 4, 5, 6, 7) neutron scattering, 8) transport, 9, 10) optical spectrum, 11) electronic specific heat, 12) density of states 13) and the single particle spectral weight. 14) The experimental results are reviewed in ref.…”

Section: §1 Introductionmentioning

confidence: 99%

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

2001

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The pseudogap phenomena in High-Tc cuprates are investigated on the basis of the Hubbard model which includes only the on-site repulsive interaction U . We consider the pairing scenario for the pseudogap. The pseudogap arises from the resonance scattering due to the strong superconducting fluctuations. First, the electronic state and the anti-ferromagnetic spin fluctuations are calculated by using the fluctuation exchange (FLEX) approximation. The T-matrix which is the propagator of the superconducting fluctuations is calculated by extending theÉliashberg equation. The characteristics of the superconducting fluctuations due to the pairing interaction arising from the spin fluctuations are represented in the T-matrix. The self-energy due to the superconducting fluctuations is calculated by the T-matrix approximation. The pseudogap is shown in the single particle properties and the magnetic properties. Moreover, a comprehensive explanation of the doping dependence of the pseudogap is obtained. Furthermore, we apply the theory to the electron-doped cuprates and obtain the consistent results with the recent experiments. Finally, the self-consistent calculation for the spin fluctuations, superconducting fluctuations and the single particle properties are carried out within the FLEX and the self-consistent T-matrix approximations. The relation between the superconducting fluctuations and the spin fluctuations are clarified. The calculated superconducting critical temperature Tc is remarkably reduced from the results of the mean field (FLEX) calculation. In particular, it is shown that the critical temperature decreases with decreasing doping in the under-doped region with large U . The pseudogap phenomena in under-doped High-T c cuprates have been interested for many years. The pseudogap is considered to be a key issue for the comprehensive understanding of the High-T c superconductivity.The pseudogap phenomena mean the suppression of the spectral weight above T c without any long range order. They are universal phenomena observed in various compounds of High-T c cuprates in the under-doped region. First, the pseudogap was found in the magnetic excitation channel by the nuclear magnetic resonance (NMR) experiment. 1) At present, the pseudogap phenomena have been observed in various quantities which include NMR, 1, 2, 3, 4, 5, 6, 7) neutron scattering, 8) transport, 9, 10) optical spectrum, 11) electronic specific heat, 12) density of states 13) and the single particle spectral weight. 14) The experimental results are reviewed in ref. 15.There are many theoretical scenarios proposed for the pseudogap phenomena. An important one is the resonating valence bond (RVB) theory. The RVB theory is an approach from the non-Fermi liquid state and attributes the pseudogap to the singlet pairing of the spinons. 16) As an approach from the Fermi liquid state, the magnetic * E-mail: yanase@hosi.phys.s.u-tokyo.ac.jp * * Present address: Department of Physics, University of Tokyo, Tokyo 113-0033 scenario has been investigated. 17,18) ...

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“…1(a) and 1(b) suggests the possibility that T c in HTSC systems may also be determined by n s /m * at T → 0 averaged over a length scale of several times ξ ab . Figure 2(a) compares the doping dependence of n s /m * from µSR [11] with that of the "gapped" response γ s in the T-linear term γ of the specific heat [25], observed in Tl2201. The normal state value γ n in Tl2201 above T c is virtually independent of doping, which implies no doping dependence of m * ∝ γ.…”

mentioning

confidence: 99%

Microscopic phase separation in the overdoped region of high-Tc cuprate superconductors

Uemura

2001

Solid State Communications

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We propose a phenomenological model for high-Tc superconductors (HTSC) assuming: (1) a microscopic phase separation between superconducting and normal-metal areas in the overdoped region; and (2) existence of a homogeneous superconducting phase only below the pseudo-gap T * line, which shows a sharp reduction towards T * ∼ 0 at a mildly overdoped critical concentration xc. This model explains anomalous doping and temperature dependences of ns/m * (superconducting carrier density / effective mass) observed in several overdoped HTSC systems. We point out an analogy to superfluid 4 He/ 3 He films, and discuss an energetic origin of microscopic phase separation. 74.25.Dw, Since the discovery of high-T c cuprate superconductors (HTSC), accumulated studies have revealed unusual phenomena in the underdoped (UD) region, such as, correlations between T c and n s /m * (superconducting carrier density / effective mass) at T → 0 shown by measurements of the magnetic field penetration depth λ [1], and the pseudo-gap phenomena [2]. These results stimulated development of various theories / models for condensation, including Bose-Einstein (BE) to BCS crossover [3,4], phase fluctuations [5,6], XY-model [7] and BE condensation [8]. These models [3][4][5][6][7][8] assume the existence of pre-formed charge pairs above T c . Different pictures, however, assume single charge above T c based on the resonating-valence-bond concepts [9,10].Several anomalous results have been found also in the overdoped (OD) region: µSR studies on Tl 2 Ba 2 CuO 6+δ (Tl2201) [11,12] revealed that n s /m * at T → 0 decreases with increasing hole doping. This tendency has been observed subsequently in thin film La 2−x Sr x CuO 4 (LSCO) [13] and bulk YBa 2 Cu 3 O y (YBCO) [14] systems in the OD region. The "coherence peak" in ARPES spectra [15] also follows this behavior of n s /m * in the OD region. Meanwhile, Tallon and Loram [16] noticed a sharp reduction of the pseudo-gap T * line in the temperature T vs. hole-concentration x phase diagram heading towards T * ∼ 0 at a critical concentration x c ∼ 0.19 holes/Cu which lies in the mildly OD region. In view of the existence of superconductivity in x > x c where the T * line does not exist, Tallon and Loram [16] have advocated a view point that the pseudogap phenomena is not representing pre-cursor superconducting phenomena, but should be ascribed to a tendency towards a ground state competing with superconductivity.We have, however, suggested another possible view point in which T * is ascribed to a signature of a gradual pre-formation of pairs [4] while the anomaly in the OD region to a phase separation [4,11,17,18]. In the present paper, resorting to a model-calculation of n s /m * , comparison with experimental results, a crude estimate of competing electrostatic and condensation/pairing energies, and analogy to 4 He/ 3 He films, we demonstrate that our picture with microscopic phase separation between superconducting and normal-metal regions can quantitatively account for several anomalous results in ...

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The electronic specific heat of cuprate superconductors

Cited by 315 publications

References 8 publications

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

Microscopic phase separation in the overdoped region of high-Tc cuprate superconductors

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The electronic specific heat of cuprate superconductors

Cited by 315 publications

References 8 publications

Condensation, excitation, pairing, and superfluid density in high-Tc superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-Tc superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-TcCuprates

Microscopic phase separation in the overdoped region of high-Tc cuprate superconductors

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Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates