PHYSICS/BK21 SEMINAR[09.06.10 ]pm2:00~
관련링크
본문
"
“Spectroscopic Fingerprint of Phase Incoherent
Superconductivity in the Pseudogap State of
Underdoped Bi2Sr2CaCu2O8+δ”
♦Speaker : Dr. Jhinhwan Lee (Cornell University)
♦Place : Physics Seminar Room (Science Bldg, 3-201)
♦Date & Time : June, 10(Wed) 2:00 ~ 3:00 pm
Abstract
One possible explanation for the mysterious ‘pseudogap’ state of the hole-doped cuprate superconductors
is that it is a d-wave superconductor but without quantum phase rigidity. While several transport and
thermodynamic studies indicate this to be true for some regions of the phase diagram, unanimity on the
extent of these regions is lacking. Thus the spectroscopic ‘fingerprint’ of phase incoherent superconductivity
would be invaluable to determine precisely where this state occurs. One spectroscopic signature of d-wave
superconductivity is the particle-hole symmetric ‘octet’ of dispersive Bogoliubov quasiparticle interference
(QPI) modulations. In this presentation I will report the temperature dependence of the complete QPI octet
from low temperatures to well into the pseudogap regime. Remarkably, we find no dramatic changes in the
QPI octet phenomenology at the superconductor’s critical temperature Tc and, indeed, show that it exists at
all temperatures up to at least T ~ 1.5Tc. Thus, our data provide direct spectroscopic evidence for phase
incoherent superconductivity in the underdoped pseudogap regime and also a new perspective on the
temperature evolution of the superconducting energy gap. Moreover, they reveal that the pseudogap
electronic structure consists of three distinct elements: the Fermi arc, the gap to coherent k-space
excitations of a phase disordered d-wave superconductor, and the gap to non-dispersive locally symmetry
breaking excitations at the pseudogap energy scale. I will also address in detail the technical challenges in
the high-precision variable-temperature QPI measurement and present a new cross-sectional QPI analysis
scheme that can be used to more accurately determine the Green’s function and the scattering matrix
elements. Together they will form the technological basis of mapping the Green’s function and the scattering
matrix elements over the entire phase diagram of an unknown material.
Contact Person : Prof. Ki Bong Lee(054-279-2068, kibong@postech.ac.kr)
"
“Spectroscopic Fingerprint of Phase Incoherent
Superconductivity in the Pseudogap State of
Underdoped Bi2Sr2CaCu2O8+δ”
♦Speaker : Dr. Jhinhwan Lee (Cornell University)
♦Place : Physics Seminar Room (Science Bldg, 3-201)
♦Date & Time : June, 10(Wed) 2:00 ~ 3:00 pm
Abstract
One possible explanation for the mysterious ‘pseudogap’ state of the hole-doped cuprate superconductors
is that it is a d-wave superconductor but without quantum phase rigidity. While several transport and
thermodynamic studies indicate this to be true for some regions of the phase diagram, unanimity on the
extent of these regions is lacking. Thus the spectroscopic ‘fingerprint’ of phase incoherent superconductivity
would be invaluable to determine precisely where this state occurs. One spectroscopic signature of d-wave
superconductivity is the particle-hole symmetric ‘octet’ of dispersive Bogoliubov quasiparticle interference
(QPI) modulations. In this presentation I will report the temperature dependence of the complete QPI octet
from low temperatures to well into the pseudogap regime. Remarkably, we find no dramatic changes in the
QPI octet phenomenology at the superconductor’s critical temperature Tc and, indeed, show that it exists at
all temperatures up to at least T ~ 1.5Tc. Thus, our data provide direct spectroscopic evidence for phase
incoherent superconductivity in the underdoped pseudogap regime and also a new perspective on the
temperature evolution of the superconducting energy gap. Moreover, they reveal that the pseudogap
electronic structure consists of three distinct elements: the Fermi arc, the gap to coherent k-space
excitations of a phase disordered d-wave superconductor, and the gap to non-dispersive locally symmetry
breaking excitations at the pseudogap energy scale. I will also address in detail the technical challenges in
the high-precision variable-temperature QPI measurement and present a new cross-sectional QPI analysis
scheme that can be used to more accurately determine the Green’s function and the scattering matrix
elements. Together they will form the technological basis of mapping the Green’s function and the scattering
matrix elements over the entire phase diagram of an unknown material.
Contact Person : Prof. Ki Bong Lee(054-279-2068, kibong@postech.ac.kr)
"
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