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Schneider, T.

doi:10.1103/physrevb.83.144527

Cited by 7 publications

(7 citation statements)

References 45 publications

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“…The H dependence of M d , the diamagnetic component of magnetization, is very similar to that of N sc (ref. 21), as expected theoretically 16,22 . Magnetization data on an underdoped sample of Bi-2201 with T c = 12 K (ref.…”

Section: Nernst Effect and Diamagnetism In Bi-2201supporting

confidence: 50%

Decrease of upper critical field with underdoping in cuprate superconductors

et al. 2012

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It is still unclear why the transition temperature T c of cuprate superconductors falls with underdoping. The doping dependence of the critical magnetic field H c2 is directly relevant to this question, but different estimates of H c2 are in sharp contradiction. We resolve this contradiction by tracking the characteristic field scale of superconducting fluctuations as a function of doping, via measurements of the Nernst effect in La 1.8−x Eu 0.2 Sr x CuO 4 . H c2 is found to fall with underdoping, with a minimum where stripe order is strong. The same non-monotonic behaviour is observed in the archetypal cuprate superconductor YBa 2 Cu 3 O y . We conclude that competing states such as stripe order weaken superconductivity and cause both H c2 and T c to fall as cuprates become underdoped.T wo paradigms have been proposed to account for the dome-like region of superconductivity in the temperaturedoping phase diagram of cuprate superconductors 1 . In the first, the amplitude of the superconducting order parameter grows monotonically as the doping p is reduced, but its phase is increasingly disordered 2 , causing T c to fall at low p. The signature of this scenario is strong phase fluctuations and a superconducting gap above T c in the underdoped regime. In the second paradigm, the fall of T c at low p is due to the onset of a state that competes with superconductivity. The signature of this scenario is a small superconducting gap and a small H c2 in the underdoped regime.Whether strong phase fluctuations or a decrease in the pairing gap is causing T c to fall in underdoped cuprates is currently an open question. Different interpretations of photoemission data disagree on the evolution of the pairing gap 3-6 and different estimates of the upper critical field H c2 are in sharp contradiction 7,8 . The Nernst signal observed above T c in underdoped cuprates has been attributed to superconducting fluctuations 8-10 , and because it persists up to temperatures several times T c , it was deemed incompatible with the standard Gaussian fluctuations of the superconducting order parameter. It was attributed instead to vortex-like excitations in a phase-fluctuating superconductor 9,10 with a non-zero pairing amplitude above T c . The critical field H c2 deduced from the Nernst data on cuprates such as Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) was reported to increase with underdoping 8 , even though T c falls. As shown in Fig. 1a, this is in striking contrast to the rapid drop in H c2 deduced from a Gaussian analysis of fluctuations in the magneto-conductivity of YBa 2 Cu 3 O y (YBCO; ref. 7). Nernst effect in Eu-LSCOHere we re-examine the Nernst effect in cuprates with a study of La 1.8−x Eu 0.2 Sr x CuO 4 (Eu-LSCO), an underdoped cuprate in which the ratio of superconducting (N sc ) to quasiparticle (N qp ) contributions to the Nernst signal N is exceptionally large-at

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Section: Nernst Effect and Diamagnetism In Bi-2201supporting

confidence: 50%

Decrease of upper critical field with underdoping in cuprate superconductors

et al. 2012

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“…Scanning tunneling spectroscopy studies 135,136 of Bi 2 Sr 2 CaCu 2 O 8+δ have indicated a granular character to superconducting correlations above T c , and a scanning magnetometry study 137 of an LSCO film found inhomogeneous magnetic domains that survived to T c + 60 K. The electronic inhomogeneity may be a necessary ingredient to explain the large magnitude of ρ ab in the normal state. Indeed, Schneider and Weyeneth 138 have recently presented an analysis of the diamagnetism and Nernst signal based on a granular picture. Similarly, there has been an estimate of the diamagnetism from fluctuating stripes.…”

Section: 128mentioning

confidence: 99%

Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu
Wen
¹
,
Xu
²
,
Xu
³

et al. 2012
Phys. Rev. B
25
6
38
0
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The superconducting system La2−xBaxCuO4 is known to show a minimum in the transition temperature, Tc, at x = 1 8 where maximal stripe order is pinned by the anisotropy within the CuO2 planes that occurs in the low-temperature-tetragonal (LTT) crystal structure. For x = 0.095, where Tc reaches its maximum value of 32 K, there is a roughly coincident structural transition to a phase that is very close to LTT. Here we present a neutron scattering study of the structural transition, and demonstrate how features of it correlate with anomalies in the magnetic susceptibility, electrical resistivity, thermal conductivity, and thermoelectric power. We also present measurements on a crystal with 1% Zn substituted for Cu, which reduces Tc to 17 K, enhances the spin stripe order, but has much less effect on the structural transition. We make the case that the structural transition correlates with a reduction of the Josephson coupling between the CuO2 layers, which interrupts the growth of the superconducting order. We also discuss evidence for two-dimensional superconducting fluctuations in the normal state, analyze the effective magnetic moment per Zn impurity, and consider the significance of the anomalous thermopower often reported in the stripeordered phase.

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“…However, it should be kept in mind that the observed strong diamagnetism and Nernst signal in a wide temperature window above T c exceeds the fluctuation dominated regime drastically. Indeed, taking the inhomogeneities of single crystals into account, the effective dimensionality is reduced to zero and reduced dimensionality enhances the thermal fluctuations [42]. Nonetheless, the proven existence of copper pairs above T c implies that they contribute to the transport properties and with that modify the standard Fermi liquid picture.…”

Section: Discussionmentioning

confidence: 99%

Quantum phase transition in overdoped La$_{2-x}$Sr$_x$CuO$_4$ evinced by the superfluid density

Schneider

2021

Preprint

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The superfluid density ρ sf (T ) = λ −2 (T ) of overdoped La2−xSrxCuO4 thin films of high quality have been measured with Tc (defined by the onset of the Meissner effect ) from 5.1 to 41.6 K by Božović et al. [1]. Given this Tc the superfluid density ρ sf (T ) shows no clear evidence of critical fluctuations and no indication of vortex unbinding as T → Tc. Nevertheless, ρ sf (T ) displays the behavior expected for a quantum phase transition (QPT) in the (3 + 1)D-xy dimensional universality class, with ρ sf (T ) ∝ T −2 c as T → 0. However, this relation is also a hallmark of dirty superconductors, treated in the mean-field approximation. Here we attempt to clear out the nature of the suppression of ρ sf (T ) as Tc → 0. Noting that for any finite system the continuous transition will be rounded we perform a finite size scaling analysis. It uncovers that the ρ sf (T ) data are consistent with a finite length limited 3D-xy transition. In some films it is their thickness and in others their inhomogeneity that determines the limiting length. Having established the precondition for the occurrence of a QPT mapping on the (3 + 1)D-xy model, we explore the consistency with the hallmarks of this transition. In particular with the relations ρ sf (T ) /ρ s (0) = 1 − ycT /Tc, Tc ∝ 1/λ (0) as Tc → 0 and yc = αλ 2 (0) Tc, where α is the coefficient in ρ sf (T ) = ρ s (0) − αT . The emerging agreement with these characteristics points clearly to a quantum fluctuations induced suppression, revealing the crossover from the thermal to the quantum critical regime as Tc → 0. In the classical-quantum mapping it corresponds to a 3D to (3 + 1)D crossover.

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Diamagnetism, Nernst signal, and finite-size effects in superconductors above the transition temperatureTc

Cited by 7 publications

References 45 publications

Decrease of upper critical field with underdoping in cuprate superconductors

Decrease of upper critical field with underdoping in cuprate superconductors

Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu
Wen
¹
,
Xu
²
,
Xu
³

et al. 2012
Phys. Rev. B
25
6
38
0
View full text Add to dashboard Cite

Quantum phase transition in overdoped La$_{2-x}$Sr$_x$CuO$_4$ evinced by the superfluid density

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Diamagnetism, Nernst signal, and finite-size effects in superconductors above the transition temperatureTc

Cited by 7 publications

References 45 publications

Decrease of upper critical field with underdoping in cuprate superconductors

Decrease of upper critical field with underdoping in cuprate superconductors

Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095CuWen1, Xu2, Xu3 et al. 2012Phys. Rev. B256380View full textAdd to dashboardCite

Quantum phase transition in overdoped La$_{2-x}$Sr$_x$CuO$_4$ evinced by the superfluid density

Contact Info

Product

Resources

About

Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu
Wen
¹
,
Xu
²
,
Xu
³

et al. 2012
Phys. Rev. B
25
6
38
0
View full text Add to dashboard Cite