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SUMMARY:What governs Tcmax in HTS cuprates? - magnetic versus dielectric p
 airing
DTSTART:20120829T110000
DTSTAMP:20260427T221733Z
UID:e7b43014d0191e00e538643990f14dcf54dec824308d99941e39bfce
CATEGORIES:Conferences - Seminars
DESCRIPTION:J. L. Tallon\, MacDiarmid Institute for Advanced Materials and
  Nanotechnology\, Industrial Research Limited\, P.O. Box 31310\, Lower Hut
 t\, New Zealand\nThe mechanism that pairs electrons in cuprate superconduc
 tors remains uncertain\, though it is widely believed to be magnetic. If s
 o\, the energy scale for the pairing boson and hence for Tc is governed to
  leading order by J\, the antiferromagnetic exchange interaction. We vary 
 J (as measured by two-magnon Raman scattering) by more than 160% by changi
 ng ion sizes in LnA2Cu3O7-δ where A=(Ba\,Sr) and Ln=(La\, … Lu). Such c
 hanges are often referred to as “internal” pressure. Surprisingly\, we
  find Tcmax anticorrelates with J. This is opposite to the effect of exter
 nal pressure\, suggesting that J is not the dominant energy scale governin
 g Tcmax. In contrast\, we show there is a clear correlation between Tcmax 
 and the sum of polarisabilities of the constituent ions\, weighted by thei
 r densities. An immediate consequence is the possibility of a pairing mech
 anism having its origin with quantized waves of electronic polarization.\n
 This is a talk in two parts. First\, I will briefly review where we in New
  Zealand have got to in manufacturing a broad range of high-Tc products. T
 hen I will address the topic of the title.
LOCATION:PH L1 503 http://plan.epfl.ch/?lang=en&room=PH.L1.503
STATUS:CONFIRMED
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