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BEGIN:VEVENT
DTSTAMP:20260811T223644Z
LAST-MODIFIED:20130214T185340Z
DTSTART:20130226T203000Z
DTEND:20130226T213000Z
UID:event973@bu.edu
URL:http://physics.bu.edu/internal/events/show/973
SUMMARY:Superconductivity: the Gift that Keeps on Giving
DESCRIPTION:Featuring Peter Johnson\, BNL\nHosted by: Kevin Smith\nPoster: 
	http://physics.bu.edu/posters/2013_Spring/06_Johnson.pdf\n\nPart of the Phy
	sics Department Colloquia Series.\n\nAbstract:\nSuperconductivity\, first d
	iscovered at the beginning of the twentieth century\, has presented new cha
	llenges for the physics community ever since.  Most recently the discovery 
	of high superconducting transition temperatures in the ceramic copper oxide
	s has lead to the opening of new fields of research into the properties of 
	so-called strongly correlated electron materials.  Unlike metallic systems 
	where the coulombic effects are highly screened\, the strong forces between
	 electrons in these new materials lead to a whole range of poorly understoo
	d phenomena.  High resolution photoemission is one probe of these propertie
	s that has added considerably to our knowledge base.   Indeed the technique
	 is recognized as one of the most powerful probes of the electronic structu
	re in condensed matter systems.  In the present talk we focus on studies of
	 the high Tc superconductors.  In the under-doped or pseudo-gap phase of th
	e cuprate superconductors\, a significant portion of the Fermi surface is s
	till gapped at temperatures above the transition temperature Tc. Further in
	stead of a closed Fermi surface\, photoemission studies indicate that the l
	ow-energy electronic excitations appear to form Fermi arcs separated by gap
	ped regions.  Here we show that the Fermi arcs may in fact be one side of F
	ermi pockets\, consistent with the underlying nature of the spin liquids in
	 these materials and indeed consistent with the fact that these materials a
	re doped Mott insulators.  By examining a range of reduced doping levels do
	wn into the non-superconducting regime it appears that the areas of the hol
	e pockets scale with the doping level.  A particle-hole asymmetry observed 
	in the nodal region is clear evidence that electron pairing does not origin
	ate from the Fermi arcs in the normal state. However in contrast the partic
	le-hole symmetry observed in the anti-nodal region is interpreted as eviden
	ce for singlet pairs forming along the copper-oxygen bond directions at tem
	peratures above the superconducting transition temperature Tc.   We also di
	scuss studies of the recently discovered Fe based superconductors.  We exam
	ine possible sources of the quasi one dimensionality or nematicity in these
	 materials and also discuss pressure dependent effects on the Fermi surface
	.
LOCATION:SCI 109\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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