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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.


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The crystal structure of YBa2Cu3O6+x.
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f1: The crystal structure of YBa2Cu3O6+x.

Mentions: Different origins have been proposed to explain the PPC, which can be generally divided into two main lines: (a) Photo-induced charge transfer and (b) photo-assisted oxygen ordering. The underlying mechanisms can only be understood by taking into account the anisotropic structure of YBCO. In contrast to most other cuprate systems, YBCO consists of CuO2 planes separated by CuOx layers which form Cu-O chains along the crystallographic b axis at higher doping levels x (Fig. 1). At low x the oxygen atoms in these CuOx layers are isolated from each other9. Longer Cu-O chains form at higher x, leading to the formation of localized holes in the CuOx layers. This results in a charge transfer of electrons from the CuO2 planes to the Cu-O chains increasing the number of mobile holes in the CuO2 planes. Therefore, the ordering of oxygen in the CuOx layers plays a major role for conductivity as well as for superconductivity in YBCO. A longer average chain length leads to a higher charge carrier density in the CuO2 planes and to a higher Tc12 on the underdoped side of the phase diagram.


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)

The crystal structure of YBa2Cu3O6+x.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: The crystal structure of YBa2Cu3O6+x.
Mentions: Different origins have been proposed to explain the PPC, which can be generally divided into two main lines: (a) Photo-induced charge transfer and (b) photo-assisted oxygen ordering. The underlying mechanisms can only be understood by taking into account the anisotropic structure of YBCO. In contrast to most other cuprate systems, YBCO consists of CuO2 planes separated by CuOx layers which form Cu-O chains along the crystallographic b axis at higher doping levels x (Fig. 1). At low x the oxygen atoms in these CuOx layers are isolated from each other9. Longer Cu-O chains form at higher x, leading to the formation of localized holes in the CuOx layers. This results in a charge transfer of electrons from the CuO2 planes to the Cu-O chains increasing the number of mobile holes in the CuO2 planes. Therefore, the ordering of oxygen in the CuOx layers plays a major role for conductivity as well as for superconductivity in YBCO. A longer average chain length leads to a higher charge carrier density in the CuO2 planes and to a higher Tc12 on the underdoped side of the phase diagram.

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