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DTSTAMP:20260909T182822Z
LAST-MODIFIED:20121116T203436Z
DTSTART:20070323T160000Z
DTEND:20070323T180000Z
UID:event99@bu.edu
URL:http://physics.bu.edu/internal/events/show/99
SUMMARY:Point-contact spectroscopy of heavy-fermion superconductors and met
	als
DESCRIPTION:Featuring Wan Kyu Park\, University of Illinois\, Urbana-Champa
	ign\n\nPart of the Biophysics/Condensed Matter Seminar Series.\n\nIdentifyi
	ng the order parameters in a superconductor is a crucial step toward an elu
	cidation of the underlying pairing mechanism. The recently discovered heavy
	-fermion compounds CeTIn5 (T = Co\, Rh\, Ir) and their doped variants have 
	attracted a great deal of interest due to their novel and rich physical pro
	perties\, including coexistence of superconductivity and magnetism\, quantu
	m criticality\, and intrinsically inhomogeneous superconductivity. We have 
	employed a point-contact Andreev reflection spectroscopy technique [1] in o
	rder to investigate the detailed order parameter structures in these heavy 
	fermions. This is a proven technique probing the Andreev reflection process
	\, which is a retro-reflection of an injected electron as a hole at a norma
	l-metal/superconductor interface\, transferring a Cooper pair and doubling 
	the electrical conductance in an ideal setting. In this talk\, I will prese
	nt our recent point-contact spectroscopy results on heavy-fermion supercond
	uctors\, pure and Cd-doped CeCoIn5\, and heavy-fermion metals such as CeCoI
	n5 above its Tc (= 2.3 K)\, CeRhIn5\, and YbAl3. Our Andreev conductance da
	ta on CeCoIn5 junctions along three major crystallographic orientations pro
	vide the first spectroscopic evidence for dx2-y2 symmetry of the supercondu
	cting order parameter in this compound. Andreev signal in CeCoIn5 appears h
	eavily reduced\, similar to those in other heavy-fermion superconductors bu
	t in contrast to that in Nb probed by using heavy-fermion metals. Asymmetry
	 in the background conductance is observed in all junctions involving heavy
	-fermions although it differs in material-dependent detail. Physical explan
	ations for these behaviors will be given in the context of a two-fluid mode
	l [3] and an energy-dependent density of states in heavy fermions. Conducta
	nce spectra on 10% Cd-doped CeCoIn5 exhibit intriguing behaviors as a funct
	ion of temperature and magnetic field\, undergoing antiferromagnetic and su
	perconducting transitions. Their implications will be discussed in terms of
	 competing or coexisting electronic phases.\n\n[1] W. K. Park and L. H. Gre
	ene\, Rev. Sci. Instrum. 77\, 023905 (2006). [2] W. K. Park et al.\, Phys. 
	Rev. B 72\, 052509 (2005); cond-mat/0507353; cond-mat/0606535; W. K. Park a
	nd L. H. Greene\, Phys. Rev. Lett. 96\, 259702 (2006). [3] S. Nakatsuji\, D
	. Pines and Z. Fisk\, Phys. Rev. Lett. 92\, 016401 (2004).\n\nIn collaborat
	ion with Heiko Stalzer\, Laura Greene\, John Sarrao\, Joe Thompson\, Long P
	ham\, Zachary Fisk\, Josh Frederick\, Paul Canfield.\n\nPizza at 11:30 AM
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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