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Controlling the near-surface superfluid density in underdoped YBa2Cu3O(6+x) by photo-illumination.

Stilp E, Suter A, Prokscha T, Salman Z, Morenzoni E, Keller H, Pahlke P, Hühne R, Bernhard C, Liang R, Hardy WN, Bonn DA, Baglo JC, Kiefl RF - Sci Rep (2014)

Bottom Line: Furthermore, systematic investigations in underdoped YBa2Cu3O(6+x) (YBCO) have shown an enhanced critical temperature Tc.Until now, studies of photo-persistent conductivity (PPC) have been limited to investigations of structural and transport properties, as well as the onset of superconductivity.Here we show how changes in the magnetic screening profile of YBCO in the Meissner state due to PPC can be determined on a nanometer scale utilizing low-energy muons.

View Article: PubMed Central - PubMed

Affiliation: 1] Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland [2] Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.

ABSTRACT
The interaction with light weakens the superconducting ground state in classical superconductors. The situation in cuprate superconductors is more complicated: illumination increases the charge carrier density, a photo-induced effect that persists below room temperature. Furthermore, systematic investigations in underdoped YBa2Cu3O(6+x) (YBCO) have shown an enhanced critical temperature Tc. Until now, studies of photo-persistent conductivity (PPC) have been limited to investigations of structural and transport properties, as well as the onset of superconductivity. Here we show how changes in the magnetic screening profile of YBCO in the Meissner state due to PPC can be determined on a nanometer scale utilizing low-energy muons. The data obtained reveal a strongly increased superfluid density within the first few tens of nanometers from the sample surface. Our findings suggest a non-trivial modification of the near-surface band structure and give direct evidence that the superfluid density of YBCO can be controlled by light illumination.

No MeSH data available.


Related in: MedlinePlus

Modifications of the magnetic screening profile due to illumination.The magnetic penetration profile  along the crystallographic c axis normalized to the applied magnetic field Bext of thin-film YBa2Cu3O6.42 (a), thin-film YBa2Cu3O6.67 (b), and detwinned YBa2Cu3O6.67 single crystals in the ortho-VIII phase for Bext applied parallel to the crystallographic a axis (c) and for Bext parallel to the b axis (d). The applied magnetic field Bext and the temperature are given in each figure. The presented field profiles correspond to the initial state (blue diamonds, before illumination), to the illuminated state (red circles, after illumination) and the recovered state (black triangles, after heating up to room temperature for about one day). The pronounced changes of the  profiles (in magnitude and shape) due to visible light illumination are caused by a substantial increase of the superfluid density on the nanometer length scale to the vacuum interface.
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f2: Modifications of the magnetic screening profile due to illumination.The magnetic penetration profile along the crystallographic c axis normalized to the applied magnetic field Bext of thin-film YBa2Cu3O6.42 (a), thin-film YBa2Cu3O6.67 (b), and detwinned YBa2Cu3O6.67 single crystals in the ortho-VIII phase for Bext applied parallel to the crystallographic a axis (c) and for Bext parallel to the b axis (d). The applied magnetic field Bext and the temperature are given in each figure. The presented field profiles correspond to the initial state (blue diamonds, before illumination), to the illuminated state (red circles, after illumination) and the recovered state (black triangles, after heating up to room temperature for about one day). The pronounced changes of the profiles (in magnitude and shape) due to visible light illumination are caused by a substantial increase of the superfluid density on the nanometer length scale to the vacuum interface.

Mentions: LE-µSR is an unique and powerful technique to measure non-trivial B(z) on a nanometer scale in a wide variety of superconducting single crystals18, thin films1920, and heterostructures2122, allowing also the observation of non-local effects232425. Positively charged muons are slowed down and implanted into the samples at different mean implantation depths (Figs. 2 and 3). The Larmor frequency of the muons, ωL(z), directly related to the local magnetic field B at the muon stopping site (ωL = γµB with the muon gyromagnetic moment γµ = 2π · 135.5 MHz/T), is measured via the decay positron. For a semi-infinite sample, the London equation yields a magnetic penetration profile B (z) = Bext · exp (−z/λL), for the boundary condition B(z = 0) = Bext. Therefore, measuring B (z) allows one to determine the magnetic penetration depth λL and thereby the superfluid density 26. The process cycle and the conditions of the LE-µSR measurements are presented schematically in Fig. 3. The in-situ illumination setup is described in detail in the supplementary section S1.


Controlling the near-surface superfluid density in underdoped YBa2Cu3O(6+x) by photo-illumination.

Stilp E, Suter A, Prokscha T, Salman Z, Morenzoni E, Keller H, Pahlke P, Hühne R, Bernhard C, Liang R, Hardy WN, Bonn DA, Baglo JC, Kiefl RF - Sci Rep (2014)

Modifications of the magnetic screening profile due to illumination.The magnetic penetration profile  along the crystallographic c axis normalized to the applied magnetic field Bext of thin-film YBa2Cu3O6.42 (a), thin-film YBa2Cu3O6.67 (b), and detwinned YBa2Cu3O6.67 single crystals in the ortho-VIII phase for Bext applied parallel to the crystallographic a axis (c) and for Bext parallel to the b axis (d). The applied magnetic field Bext and the temperature are given in each figure. The presented field profiles correspond to the initial state (blue diamonds, before illumination), to the illuminated state (red circles, after illumination) and the recovered state (black triangles, after heating up to room temperature for about one day). The pronounced changes of the  profiles (in magnitude and shape) due to visible light illumination are caused by a substantial increase of the superfluid density on the nanometer length scale to the vacuum interface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150113&req=5

f2: Modifications of the magnetic screening profile due to illumination.The magnetic penetration profile along the crystallographic c axis normalized to the applied magnetic field Bext of thin-film YBa2Cu3O6.42 (a), thin-film YBa2Cu3O6.67 (b), and detwinned YBa2Cu3O6.67 single crystals in the ortho-VIII phase for Bext applied parallel to the crystallographic a axis (c) and for Bext parallel to the b axis (d). The applied magnetic field Bext and the temperature are given in each figure. The presented field profiles correspond to the initial state (blue diamonds, before illumination), to the illuminated state (red circles, after illumination) and the recovered state (black triangles, after heating up to room temperature for about one day). The pronounced changes of the profiles (in magnitude and shape) due to visible light illumination are caused by a substantial increase of the superfluid density on the nanometer length scale to the vacuum interface.
Mentions: LE-µSR is an unique and powerful technique to measure non-trivial B(z) on a nanometer scale in a wide variety of superconducting single crystals18, thin films1920, and heterostructures2122, allowing also the observation of non-local effects232425. Positively charged muons are slowed down and implanted into the samples at different mean implantation depths (Figs. 2 and 3). The Larmor frequency of the muons, ωL(z), directly related to the local magnetic field B at the muon stopping site (ωL = γµB with the muon gyromagnetic moment γµ = 2π · 135.5 MHz/T), is measured via the decay positron. For a semi-infinite sample, the London equation yields a magnetic penetration profile B (z) = Bext · exp (−z/λL), for the boundary condition B(z = 0) = Bext. Therefore, measuring B (z) allows one to determine the magnetic penetration depth λL and thereby the superfluid density 26. The process cycle and the conditions of the LE-µSR measurements are presented schematically in Fig. 3. The in-situ illumination setup is described in detail in the supplementary section S1.

Bottom Line: Furthermore, systematic investigations in underdoped YBa2Cu3O(6+x) (YBCO) have shown an enhanced critical temperature Tc.Until now, studies of photo-persistent conductivity (PPC) have been limited to investigations of structural and transport properties, as well as the onset of superconductivity.Here we show how changes in the magnetic screening profile of YBCO in the Meissner state due to PPC can be determined on a nanometer scale utilizing low-energy muons.

View Article: PubMed Central - PubMed

Affiliation: 1] Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland [2] Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.

ABSTRACT
The interaction with light weakens the superconducting ground state in classical superconductors. The situation in cuprate superconductors is more complicated: illumination increases the charge carrier density, a photo-induced effect that persists below room temperature. Furthermore, systematic investigations in underdoped YBa2Cu3O(6+x) (YBCO) have shown an enhanced critical temperature Tc. Until now, studies of photo-persistent conductivity (PPC) have been limited to investigations of structural and transport properties, as well as the onset of superconductivity. Here we show how changes in the magnetic screening profile of YBCO in the Meissner state due to PPC can be determined on a nanometer scale utilizing low-energy muons. The data obtained reveal a strongly increased superfluid density within the first few tens of nanometers from the sample surface. Our findings suggest a non-trivial modification of the near-surface band structure and give direct evidence that the superfluid density of YBCO can be controlled by light illumination.

No MeSH data available.


Related in: MedlinePlus