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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

Muon stopping profiles in YBCO.The normalized stopping distribution n(z) for positively charged muons at different implantation energies for YBCO was simulated with TRIM.SP38. The lines are guides to the eye.
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f5: Muon stopping profiles in YBCO.The normalized stopping distribution n(z) for positively charged muons at different implantation energies for YBCO was simulated with TRIM.SP38. The lines are guides to the eye.

Mentions: The positrons are preferentially emitted along the µ+ spin direction at the time of decay due to the parity violation in the weak decay. Therefore, the detection of the time difference t = te − ts between the implantation time ts and the decay time te of the µ+ allows one to determine the temporal evolution of the muon-spin polarization P(t) using the expression37: where N(t) is the number of decay positrons at time t. The scale of the counted positrons is given by N0. A is the observable decay asymmetry and NBkg is a time-independent background of uncorrelated events. More details on the LE-µSR technique are given in Refs. 16, 17. The experiments were performed in the Meissner state. After zero field cooling to 5 K, a magnetic field Bext/µ0 < Hc1 was applied parallel to the surface of the sample. The muon-spin polarization function P(t) is then given by where ϕ is the initial angle of the muon spin direction relative to the positron detector. The gyromagnetic ratio of the muon is γµ = 2π · 135.5 MHz/T. The depolarization rate σ is a measure of any inhomogeneous local magnetic field distribution at the µ+ stopping site. The muon stopping distributions n(z) (see Fig. 5) were simulated for energies in the range 5 – 25 keV using the Monte Carlo code TRIM.SP38. The reliability of these simulations has been studied in various thin films1739. The mean stopping depth of the muons in YBCO is in the range 25 – 106 nm. The corresponding mean magnetic field is . To analyse the data, the penetration profiles given in supplementary section S3 were used for B (z). The penetration depths λL were determined from global fits with the µSR data analysis software package musrfit40, where µSR spectra for different energies are analysed simultaneously.


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)

Muon stopping profiles in YBCO.The normalized stopping distribution n(z) for positively charged muons at different implantation energies for YBCO was simulated with TRIM.SP38. The lines are guides to the eye.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Muon stopping profiles in YBCO.The normalized stopping distribution n(z) for positively charged muons at different implantation energies for YBCO was simulated with TRIM.SP38. The lines are guides to the eye.
Mentions: The positrons are preferentially emitted along the µ+ spin direction at the time of decay due to the parity violation in the weak decay. Therefore, the detection of the time difference t = te − ts between the implantation time ts and the decay time te of the µ+ allows one to determine the temporal evolution of the muon-spin polarization P(t) using the expression37: where N(t) is the number of decay positrons at time t. The scale of the counted positrons is given by N0. A is the observable decay asymmetry and NBkg is a time-independent background of uncorrelated events. More details on the LE-µSR technique are given in Refs. 16, 17. The experiments were performed in the Meissner state. After zero field cooling to 5 K, a magnetic field Bext/µ0 < Hc1 was applied parallel to the surface of the sample. The muon-spin polarization function P(t) is then given by where ϕ is the initial angle of the muon spin direction relative to the positron detector. The gyromagnetic ratio of the muon is γµ = 2π · 135.5 MHz/T. The depolarization rate σ is a measure of any inhomogeneous local magnetic field distribution at the µ+ stopping site. The muon stopping distributions n(z) (see Fig. 5) were simulated for energies in the range 5 – 25 keV using the Monte Carlo code TRIM.SP38. The reliability of these simulations has been studied in various thin films1739. The mean stopping depth of the muons in YBCO is in the range 25 – 106 nm. The corresponding mean magnetic field is . To analyse the data, the penetration profiles given in supplementary section S3 were used for B (z). The penetration depths λL were determined from global fits with the µSR data analysis software package musrfit40, where µSR spectra for different energies are analysed simultaneously.

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