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UID:UW-Physics-Event-3403
DTSTART:20141002T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T171826Z
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.<br>
\n<br>
\nReferences<br>
\n[1] R. Meservey 
 et al.\, Phys. Rev. Lett. 25\, 1270 (1970).<br>
\n[2] P. M. Tedrow and
  R. Meservey\, Phys. Rev. Lett. 26\, 192 (1971). <br>
\n
URL:https://www.physics.wisc.edu/events/?id=3403
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