Josephson scanning tunneling microscopy -- a local and direct probe of the superconducting order parameter

Journal Article · Tue Sep 01 04:00:00 EDT 2009 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.80.144506· OSTI ID:974533

Kimura, Hikari; Dynes, Robert; Barber, Jr, Richard P; Ono, S; Ando, Y

Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+delta (BSCCO) samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a novel scanning tunneling microscope (STM) equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wavefunction of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors and the high transition temperature superconductors. The local relationship between the ICRN product and the quasiparticle density of states (DOS) gap are presented within the context of phase diagrams for BSCCO. Excessive current densities can be produced with these measurements and have been found to alter the local DOS in the BSCCO. Systematic studies of this effect were performed to determine the practical measurement limits for these experiments. Alternative methods for preparation of the BSCCO surface are also discussed.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Materials Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 974533
• Report Number(s): LBNL-2758E
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COHERENCE LENGTH
MICROSCOPES
ORDER PARAMETERS
PERFORMANCE
PHASE DIAGRAMS
PROBES
SCANNING TUNNELING MICROSCOPY
SPATIAL RESOLUTION
SUPERCONDUCTORS
Superconductivity
HighTc
TRANSITION TEMPERATURE
TUNNELING