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The Meissner effect in a strongly underdoped cuprate above its critical temperature.

Morenzoni E, Wojek BM, Suter A, Prokscha T, Logvenov G, Božović I - Nat Commun (2011)

Bottom Line: The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state.In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed.The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. elvezio.morenzoni@psi.ch

ABSTRACT
The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state. In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed. Here we probe the local diamagnetic response in the normal state of an underdoped La(1.94)Sr(0.06)CuO(4) layer (T(c)'≤5 K), which is brought into close contact with two nearly optimally doped La(1.84)Sr(0.16)CuO(4) layers (T(c)≈32 K). We show that the entire 'barrier' layer of thickness, much larger than the typical c axis coherence lengths of cuprates, exhibits a Meissner effect at temperatures above T(c)' but below T(c). The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation.

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Stopping profiles.Normalized muon implantation profiles in the trilayer structure La1.84Sr0.16CuO4 (46 nm)/La1.94Sr0.06CuO4 (46 nm)/La1.84Sr0.16CuO4 (46 nm) at some of the energies used. The grey shaded areas indicate the top and bottom layers of the heterostructure.
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f1: Stopping profiles.Normalized muon implantation profiles in the trilayer structure La1.84Sr0.16CuO4 (46 nm)/La1.94Sr0.06CuO4 (46 nm)/La1.84Sr0.16CuO4 (46 nm) at some of the energies used. The grey shaded areas indicate the top and bottom layers of the heterostructure.

Mentions: LE-μSR has previously been applied to obtain the depth-resolved profile of local magnetization in various thin films and heterostructures on the nm scale1112. By tuning the muon implantation energy, we vary the stopping range of the fully spin-polarized muons between 3 and 200 nm, and measure time-differential μSR spectra at different depths in the heterostructure (Fig. 1). The spectra yield information about the magnetic and superconducting properties in different layers. For instance, the observed muon spin precession frequency is directly proportional to the local magnetic field at the muon site and can detect a diamagnetic shift associated with supercurrents. In a magnetic state with a broad field distribution, one observes fast damping directly related to the width of the distribution. The technique is presented in the Methods section.


The Meissner effect in a strongly underdoped cuprate above its critical temperature.

Morenzoni E, Wojek BM, Suter A, Prokscha T, Logvenov G, Božović I - Nat Commun (2011)

Stopping profiles.Normalized muon implantation profiles in the trilayer structure La1.84Sr0.16CuO4 (46 nm)/La1.94Sr0.06CuO4 (46 nm)/La1.84Sr0.16CuO4 (46 nm) at some of the energies used. The grey shaded areas indicate the top and bottom layers of the heterostructure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104550&req=5

f1: Stopping profiles.Normalized muon implantation profiles in the trilayer structure La1.84Sr0.16CuO4 (46 nm)/La1.94Sr0.06CuO4 (46 nm)/La1.84Sr0.16CuO4 (46 nm) at some of the energies used. The grey shaded areas indicate the top and bottom layers of the heterostructure.
Mentions: LE-μSR has previously been applied to obtain the depth-resolved profile of local magnetization in various thin films and heterostructures on the nm scale1112. By tuning the muon implantation energy, we vary the stopping range of the fully spin-polarized muons between 3 and 200 nm, and measure time-differential μSR spectra at different depths in the heterostructure (Fig. 1). The spectra yield information about the magnetic and superconducting properties in different layers. For instance, the observed muon spin precession frequency is directly proportional to the local magnetic field at the muon site and can detect a diamagnetic shift associated with supercurrents. In a magnetic state with a broad field distribution, one observes fast damping directly related to the width of the distribution. The technique is presented in the Methods section.

Bottom Line: The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state.In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed.The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. elvezio.morenzoni@psi.ch

ABSTRACT
The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state. In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed. Here we probe the local diamagnetic response in the normal state of an underdoped La(1.94)Sr(0.06)CuO(4) layer (T(c)'≤5 K), which is brought into close contact with two nearly optimally doped La(1.84)Sr(0.16)CuO(4) layers (T(c)≈32 K). We show that the entire 'barrier' layer of thickness, much larger than the typical c axis coherence lengths of cuprates, exhibits a Meissner effect at temperatures above T(c)' but below T(c). The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation.

Show MeSH
Related in: MedlinePlus