Anomalous Peak in the Superconducting Condensate Density of Cuprate High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Superconductors at a Unique Doping State

Bernhard, C.; Tallon, J. L.; Bläsius, Thomas; Golnik, A.; Niedermayer, Ch.

doi:10.1103/physrevlett.86.1614

Cited by 141 publications

(169 citation statements)

References 28 publications

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“…In accord with the anti-correlation reported here between T 2 /T c0 and ρ s , one can now interpret the expansion of the fluctuation regime in irradiated YBa 2 Cu 3 O 7−δ as a direct consequence of the strong disorder-induced suppression of the superfluid density 12 , which ultimately enhances the role of phase fluctuations.…”

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confidence: 59%

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Phase-fluctuating superconductivity in overdoped La2−xSrxCuO4

Rourke

Mouzopoulou

et al. 2011

Nature Phys

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In underdoped cuprate superconductors, phase stiffness is low and long-range superconducting order is destroyed readily by thermally generated vortices (and anti-vortices), giving rise to a broad temperature regime above the zero-resistive state in which the superconducting phase is incoherent 1-4 . It has often been suggested that these vortex-like excitations are related to the normal-state pseudogap or some interaction between the pseudogap state and the superconducting state 5-10 . However, to elucidate the precise relationship between the pseudogap and superconductivity, it is important to establish whether this broad phase-fluctuation regime vanishes, along with the pseudogap 11 , in the slightly overdoped region of the phase diagram where the superfluid pair density and correlation energy are both maximal 12 . Here we show, by tracking the restoration of the normal-state magnetoresistance in overdoped La 2−x Sr x CuO 4 , that the phase-fluctuation regime remains broad across the entire superconducting composition range. The universal low phase stiffness is shown to be correlated with a low superfluid density 1 , a characteristic of both underdoped and overdoped cuprates 12-14 . The formation of the pseudogap, by inference, is therefore both independent of and distinct from superconductivity.In underdoped cuprates, an energy gap (pseudogap), of as yet unknown origin, appears in the electronic density of states well before superconductivity develops. The continuous evolution 6 of the pseudogap into the superconducting gap, combined with similarities in their gap magnitudes and symmetries 5 , has led to suggestions that the pseudogap is a precursor superconducting state 7-10 characterized by a broad temperature region over which the superconducting order parameter is finite but the phase fluctuates 3,4 . This picture of precursor pairing remains controversial however and is challenged by measurements indicating that the pseudogap itself closes at a critical doping concentration 11 , slightly beyond optimal doping, where superconductivity is most robust 12 . As it stands, there have been very few studies to date of the fluctuating superconductivity in overdoped, superconducting cuprates to establish the precise relationship between the pseudogap and phase fluctuation regimes.To address this, we focus here on the evolution of the upper critical field H c2 with temperature, as inferred by measurements of the in-plane resistivity ρ ab (T ,H ) in pulsed and d.c. magnetic fields. Previous transport studies in cuprates identified H c2 (T ) with the 'knee' at or near the top of the ρ ab (T ) curve or the temperature at which ρ ab (H ) attained a certain fraction of the normal-state value 15 . Either technique would lead to a H c2 (T ) line with a markedly different shape from that determined by the Nernst effect, for example. In this study, we adopt an alternative approach 16,17 , using the evolution of the transverse magnetoresistance ρ ab (H )(= ρ ab (H )− ρ ab (0) with H c) with temperature, field and doping, as ...

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confidence: 59%

“…Also included in Fig. 2d 12 . The clear anti-correlation between T 2 /T c0 and ρ s (p) supports the Emery-Kivelson picture 1 and provides firm evidence that the temperature interval T c0 ≤ T ≤ T 2 in overdoped cuprates is characterized by the same phase fluctuations that appear on the underdoped side.…”

mentioning

confidence: 99%

Phase-fluctuating superconductivity in overdoped La2−xSrxCuO4

Rourke

Mouzopoulou

et al. 2011

Nature Phys

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“…Remarkably, the peak spectral weight closely tracks T c , suggesting that the superconducting pairs live on the charged stripes, as predicted by several models 52,95 . Consistent with this, a number of measures of the strength of superconductivity (condensation energy, critical current) are optimized at this same point 90,6,96 where the charge stripe intensity is maximum and AFM stripes vanish. The fact that T c itself is actually optimized at a slightly lower doping may be a hint that stripes can enhance the superconducting gap, as found above, Fig.…”

Section: Doping Dependence Of Charged Stripes and Superconductivitymentioning

confidence: 72%

Phase separation models for cuprate stripe arrays

Markiewicz

Kusko

2002

Phys. Rev. B

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An electronic phase separation model provides a natural explanation for a large variety of experimental results in the cuprates, including evidence for both stripes and larger domains, and a termination of the phase separation in the slightly overdoped regime, when the average hole density equals that on the charged stripes. Several models are presented for charged stripes, showing how density waves, superconductivity, and strong correlations compete with quantum size effects (QSEs) in narrow stripes. The energy bands associated with the charged stripes develop in the middle of the Mott gap, and the splitting of these bands can be understood by considering the QSE on a single ladder.

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“…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.…”

mentioning

confidence: 89%

“…Figure 1(a) shows the results of T c versus the muon spin relaxation rate σ ∝ n s /m * at T → 0 of YBCO [1,14], Zn-doped YBCO (y = 6.7) [20] and overdoped Tl2201 [11] systems. T c increases with increasing hole doping following a linear line in the UD, a saturation in the optimal T c (OPT), and a recurring behavior in the OD region.…”

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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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Anomalous Peak in the Superconducting Condensate Density of Cuprate High-TcSuperconductors at a Unique Doping State

Cited by 141 publications

References 28 publications

Phase-fluctuating superconductivity in overdoped La2−xSrxCuO4

Phase-fluctuating superconductivity in overdoped La2−xSrxCuO4

Phase separation models for cuprate stripe arrays

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

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