BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3403
DTSTART:20141002T150000Z
DURATION:PT1H0M0S
DTSTAMP:20240319T024748Z
LAST-MODIFIED:20140924T151419Z
LOCATION:5310 Chamberlin Hall
SUMMARY:The Zeeman Effect in Confined Superconductors: A new probe of
absolute spin polarization on the atomic scale \, R. G. Herb Condensed
Matter Seminar\, Christian Ast\, Max Planck Institute for Solid State
Research
DESCRIPTION:When a dimensionally confined superconductor is subjected
to a magnetic field\, the compensating currents are suppressed such th
at superconductivity persists to much higher magnetic fields than in t
he bulk. This effect has been observed first in planar tunnel junction
s by Meservey\, Tedrow and Fulde [1]. The resulting Zeeman splitting o
f the quasiparticle density of states can be exploited as a probe for
the absolute spin polarization of a spin polarized tunnelling current
[2]. We have transferred this concept to the scanning tunnelling micr
oscope (STM) to probe the spin polarization of the tunnelling current
on the atomic scale by using a superconducting tip. As the superconduc
ting tip carries no magnetic moment itself\, the information in the sp
in polarized tunnelling current can be attributed to the magnetic prop
erties of the sample. This is a decisive advantage over other spin-pol
arized STM techniques. First measurements on magnetic cobalt islands o
n a Cu(111) substrate are in excellent agreement with literature. Meas
uring the spin polarization of the tunnelling current as a function of
tip-island distance\, we find that the spin polarization increases by
65% when the distance is increased by only 2.3Å. This can be attribu
ted to the different exponential decay of majority and minority states
into the vacuum. This means that we can exploit the vacuum barrier as
a tunable spin filter.
\n
\nReferences
\n[1] R. Meservey
et al.\, Phys. Rev. Lett. 25\, 1270 (1970).
\n[2] P. M. Tedrow and
R. Meservey\, Phys. Rev. Lett. 26\, 192 (1971).
\n
URL:https://www.physics.wisc.edu/events/?id=3403
END:VEVENT
END:VCALENDAR