AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Wednesday Sessions
       Session EM-WeM

Paper EM-WeM3
An Ultra-Thin Molecular Superconductor

Wednesday, November 11, 2009, 8:40 am, Room B1

Session: Organic & Molecular Electronics
Presenter: S.-W. Hla, Ohio University
Authors: K. Clark, Ohio University
A. Hassanien, Nanotechnology Research Institute, Japan
K.-F. Braun, Physikalisch Technische Bundesanstalt, Germany
H. Tanaka, Nanotechnology Research Institute, Japan
S.-W. Hla, Ohio University
Correspondent: Click to Email
Almost a century after its discovery by H. Kamerlingh Onnes, superconductivity continues to be an inspirational subject for many physicists because of its rich physical phenomena. Among a variety of superconducting materials, the organic superconductors are regarded as “unconventional superconductors” based on the different nature of their superconducting states as compared to the conventional BCS superconductors. A class of Bechgaard type5 charge transfer salts having a D2A arrangement, where D and A are the donor and acceptor respectively, exhibit superconductivity in the bulk. Here, we form an ultra-thin Bechgaard salt with the smallest possible molecular-unit thickness composed of just a sheet of molecular layer having individual GaCl4 molecules sandwiched between the chains of a double domino stacked BETS on a Ag(111) surface. Remarkably, scanning tunneling spectroscopy of this ultra-thin Bechgaard layer at 5.4K reveals a clear superconducting gap exhibiting d-wave pairing symmetry. Real space spectroscopic images with a molecular resolution provide an experimental paradigm: The stacked BETS chains in the layer act as the superconducting sites. In stark contrast to the high Tc superconductors, the spectroscopic maps clearly display nanoscale electronic order indicating a robust superconductivity down to an extreme spatial limit.