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    “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)바카라 확률2:00바카라 확률~바카라 확률3:00 pm

Abstract
  
One possible explanation for the mysterious ‘pseudogap’ state of the hole-doped cuprate superconductors
is that it is a d-wave superconductor바카라 확률but바카라 확률without바카라 확률quantum바카라 확률phase바카라 확률rigidity.바카라 확률While바카라 확률several바카라 확률transport바카라 확률and
thermodynamic studies indicate this to be true for some regions of the phase바카라 확률diagram,바카라 확률unanimity바카라 확률on바카라 확률the
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.바카라 확률Thus,바카라 확률our바카라 확률data provide direct spectroscopic evidence for phase
incoherent superconductivity in the underdoped바카라 확률pseudogap바카라 확률regime바카라 확률and바카라 확률also바카라 확률a바카라 확률new바카라 확률perspective on the
temperature evolution of바카라 확률the바카라 확률superconducting바카라 확률energy바카라 확률gap.바카라 확률Moreover,바카라 확률they바카라 확률reveal바카라 확률that바카라 확률the바카라 확률pseudogap
electronic structure consists바카라 확률of바카라 확률three바카라 확률distinct바카라 확률elements:바카라 확률the바카라 확률Fermi arc,바카라 확률the바카라 확률gap바카라 확률to바카라 확률coherent바카라 확률k-space
excitations of a phase disordered d-wave superconductor, and the gap to non-dispersive locally symmetry
breaking excitations at the pseudogap energy scale.바카라 확률I 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 determine바카라 확률the바카라 확률Green’s바카라 확률function바카라 확률and바카라 확률the바카라 확률scattering바카라 확률matrix
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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