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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

Shifts in the critical temperature ΔTc from resistance measurements.Resistance R versus temperature T of YBa2Cu3O6.42 (a) and YBa2Cu3O6.67 (b) thin films for the initial state (blue diamonds, before illumination), the illuminated state (red circles, after illumination at 270 K), and the recovered state (black triangles, sample kept above room temperature for about one day). The critical temperature Tc was determined as the temperature where R exceeds twice the RMS of the noise (dashed line) during heating of the samples. The shifts of the resistivity curves to lower values, after illumination at 270 K, reflect an increased charge carrier density at all temperatures T < 270 K. The arrows indicate the shifts in the transition temperatures ΔTc due to visible-light illumination.
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f4: Shifts in the critical temperature ΔTc from resistance measurements.Resistance R versus temperature T of YBa2Cu3O6.42 (a) and YBa2Cu3O6.67 (b) thin films for the initial state (blue diamonds, before illumination), the illuminated state (red circles, after illumination at 270 K), and the recovered state (black triangles, sample kept above room temperature for about one day). The critical temperature Tc was determined as the temperature where R exceeds twice the RMS of the noise (dashed line) during heating of the samples. The shifts of the resistivity curves to lower values, after illumination at 270 K, reflect an increased charge carrier density at all temperatures T < 270 K. The arrows indicate the shifts in the transition temperatures ΔTc due to visible-light illumination.

Mentions: Two sets of YBCO thin films (x = 0.42, 0.67) with twinned crystallographic a and b axes were investigated along with a detwinned single-crystal mosaic (x = 0.67). The YBCO thin film sets show shifts of ΔTc = 6.4(6) K (x = 0.42) and ΔTc = 0.9(1) K (x = 0.67) after illumination with about 7 · 1022 photons/cm2, in agreement with previous results8 (see Fig. 4). The magnetic screening profiles determined by LE-µSR show for the initial state (before illumination) an exponential decay for the single crystals and a cosh behaviour in the thin films (resulting from the exponential penetration of the magnetic field from both interfaces) as depicted in Fig. 2. After illumination, all magnetic screening profiles are shifted to lower values and exhibit a pronounced change in shape. The corresponding superfluid density ns is enhanced in all sample sets investigated.


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)

Shifts in the critical temperature ΔTc from resistance measurements.Resistance R versus temperature T of YBa2Cu3O6.42 (a) and YBa2Cu3O6.67 (b) thin films for the initial state (blue diamonds, before illumination), the illuminated state (red circles, after illumination at 270 K), and the recovered state (black triangles, sample kept above room temperature for about one day). The critical temperature Tc was determined as the temperature where R exceeds twice the RMS of the noise (dashed line) during heating of the samples. The shifts of the resistivity curves to lower values, after illumination at 270 K, reflect an increased charge carrier density at all temperatures T < 270 K. The arrows indicate the shifts in the transition temperatures ΔTc due to visible-light illumination.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Shifts in the critical temperature ΔTc from resistance measurements.Resistance R versus temperature T of YBa2Cu3O6.42 (a) and YBa2Cu3O6.67 (b) thin films for the initial state (blue diamonds, before illumination), the illuminated state (red circles, after illumination at 270 K), and the recovered state (black triangles, sample kept above room temperature for about one day). The critical temperature Tc was determined as the temperature where R exceeds twice the RMS of the noise (dashed line) during heating of the samples. The shifts of the resistivity curves to lower values, after illumination at 270 K, reflect an increased charge carrier density at all temperatures T < 270 K. The arrows indicate the shifts in the transition temperatures ΔTc due to visible-light illumination.
Mentions: Two sets of YBCO thin films (x = 0.42, 0.67) with twinned crystallographic a and b axes were investigated along with a detwinned single-crystal mosaic (x = 0.67). The YBCO thin film sets show shifts of ΔTc = 6.4(6) K (x = 0.42) and ΔTc = 0.9(1) K (x = 0.67) after illumination with about 7 · 1022 photons/cm2, in agreement with previous results8 (see Fig. 4). The magnetic screening profiles determined by LE-µSR show for the initial state (before illumination) an exponential decay for the single crystals and a cosh behaviour in the thin films (resulting from the exponential penetration of the magnetic field from both interfaces) as depicted in Fig. 2. After illumination, all magnetic screening profiles are shifted to lower values and exhibit a pronounced change in shape. The corresponding superfluid density ns is enhanced in all sample sets investigated.

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