title: Inducing superconductivity at a nanoscale: photodoping with a near-field scanning optical microscope.
abstract: The local modification of an insulating GdBa2Cu3O6.5 thin film, made superconducting by illumination with a near-field scanning optical microscope (NSOM), is reported. A 100-nm aperture NSOM probe acts as a sub-wavelength light source of wavelength lambda(exc) = 480-650 nm, locally generating photocarriers in an otherwise insulating GdBa2-Cu3O6.5 thin film. Of the photogenerated electron-hole pairs, electrons are trapped in the crystallographic lattice, defining an electrostatic confining potential to enable the holes to move. Reflectance measurements at lambda = 1.55 microm at room temperature show that photocarriers can be induced and constrained to move on a approximately 200 nm scale for all investigated lambda(exc). Photogenerated wires present a superconducting critical temperature Tc= 12 K with a critical current density Jc = 10(4) A cm(-2). Exploiting the flexibility provided by photodoping through a NSOM probe, a junction was written by photodoping a wire with a narrow (approximately 50 nm) under-illuminated gap. The strong magnetic field modulation of the critical current provides a clear signature of the existence of a Josephson effect in the junction.
authors.affiliation: Department of Physics, University of Maryland, College Park 20742, USA. rdecca@physics.umd.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Decca
authors.forename: H D
authors.initials: HD
authors.lastname: Drew
authors.forename: B
authors.initials: B
authors.lastname: Maiorov
authors.forename: J
authors.initials: J
authors.lastname: Guimpel
authors.forename: E J
authors.initials: EJ
authors.lastname: Osquiguil