The Ground State of Locally Superconducting Films Allen M. Goldman, University of Minnesota, DMR 0455121

1
The Ground State of Locally Superconducting
Films Allen M. Goldman, University of Minnesota,
DMR 0455121
The application of weak magnetic fields, B,
perpendicular to the plane of homoge-neous,
amorphous InxOy thin films exhibi-ting local
superconductivity has been found to produce a
rapid and substantial increase in resistance, R,
which reaches a maximum that increases in
magnitude and shifts to lower fields with
decreasing temperature. This decrease in the
field at the maximum implies the existence of a
length scale that diverges in the zero
temperature limit suggesting that there may be a
quantum critical point at zero field with the
ground state being an insulator. The
conductance-voltage characteristics in the
field-enhanced resistance regime at non-zero
temperature, exhibit threshold voltages
reminiscent of depinning in charge-density-wave
systems. This suggests that the ground state is a
pinned charge structure.


Atomic force microscope image of Film 2 with a
maximum vertical range of 8.5 nm and an average
feature diameter of 18 nm. The film is rough but
is continuous.
(Left) Resistance vs. magnetic field of a film.
The temperatures are 40 (top), 80, 100, 120, 130,
140, 150, 170, 180, 200, 230, 250, 300, 350, 400,
and 500 mK(bottom). (Right) The fields (left
axis) and the resistances (right axis) of the
peaks in R(B) are plotted as a function of
temperature.
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The Ground State of Locally Superconducting
FilmsAllen M. Goldman, University of Minnesota,
DMR-0455121
Societal Impact The films that are the subject
of this research are examples of highly
correlated nanostructured materials. The
fundamental understanding of the properties of
such materials is important in the broader
context of materials and devices for computing
and other forms of signal processing. In the
particular case of mesoscopic systems, exhibiting
transitions between superconducting and
insulating behavior, fundamental questions of the
establishment of phase coherence are in play,
which have relevance to the understanding of
macroscopic quantum behavior of mesoscopic
superconducting systems. These may be important
in the develop-ment of quantum computing.
Education This research was carried out by K. H.
Sarwa B. Tan and Kevin Parendo. Dr. Parendo is
now a staff member of the US Patent Office. Dr.
Tan is a postdoctoral associate at Minnesota and
a recent Ph.D. graduate of the program. Some
enabling experiments were carried out by a former
student, Melissa Eblen-Zayas, and a former
postdoctoral associate, Dr. Anand Bhattacharya.
Dr. Eblen-Zayas is currently a tenure-track
professor at Carleton College. Dr. Bhattacharya
is now a member of the permanent staff of Argonne
National Laboratory. These films were grown by
Professor Zvi Ovadyahu at the Hebrew University.
The interaction with him was a broaden-ing
experience for the participants In this work.