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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:4
UID:UW-Physics-Event-4922
DTSTART:20190329T203000Z
DURATION:PT1H0M0S
DTSTAMP:20260311T043527Z
LAST-MODIFIED:20190321T213646Z
LOCATION:2241 Chamberlin Hall
SUMMARY:Ferromagnetic Josephson Junctions for Cryogenic Memory\, Physi
 cs Department Colloquium\, Norman O. Birge\, Michigan State University
DESCRIPTION:Large-scale computing facilities and data centers are usin
 g electrical power at an ever increasing rate.  Projections suggest th
 at a future “exoscale” computer will require the power output of a
  typical nuclear power plant – clearly an untenable situation.  One 
 approach to addressing this problem is to build a computer out of all 
 superconducting elements\, which dissipate very little power.  Such a 
 computer would have to be cooled to cryogenic temperatures\, so it mus
 t be extremely energy-efficient to justify the added complexity and co
 st associated with cooling.
\n
\nSuperconducting logic circuits based 
 on manipulating single flux quanta have existed for 30 years\; what ha
 s been missing is a high-density\, fast\, and energy-efficient cryogen
 ic memory.  One approach is to use Josephson junctions containing ferr
 omagnetic (F) materials as the memory element for such a memory.  The 
 basic building block is a Josephson junction containing two ferromagne
 tic layers whose magnetization directions can be switched between bein
 g parallel or antiparallel to each other\, as in a conventional spin v
 alve.  We have demonstrated successful switching of such a junction be
 tween the “0” phase state and the “π” phase state\, from meas
 urements of two junctions in a SQUID geometry.  An alternative approac
 h is to use a Josephson junction containing three ferromagnetic layers
 \, which is designed to carry spin-triplet supercurrent.  We have also
  realized controllable 0 - π switching in such a spin-triplet junctio
 n.  At the end of the talk I’ll mention what needs to be done to tur
 n these results into a real superconducting computer. 
\n
URL:https://www.physics.wisc.edu/events/?id=4922
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