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SUMMARY:Emergence of local broken symmetries with hole-doping in Ca2-xNaxC
 uO2Cl2 - Dr. Yuki Kohsaka\, Magnetic Materials Laboratory\, RIKEN Advanced
  Science Institute\, Wako\, Saitama\, Japan
DTSTART:20091130T111500Z
DTEND:20091130T121500Z
UID:TALK21651@talks.cam.ac.uk
CONTACT:Michael Sutherland
DESCRIPTION:High-temperature superconductivity in the cuprates arises from
  carrier doping into Mott insulators. Whereas the ground states of cuprate
 s are phenomenologically conventional\, the mysterious pseudogap excitatio
 n prevents us from fully understanding the electronic evolution. Although 
 dozens of proposals to unify such complex states have been made\, consensu
 s is yet to be built. Therefore\, detecting emergence of broken symmetry a
 ssociated with the pseudogap state\, from Mott insulating state upon carri
 er doping\, is of fundamental importance to discern those proposals.\n\nSc
 anning tunneling spectroscopy provides unique capability for this purpose.
  With this technique\, we found bond-centered unidirectional electronic do
 mains\, which break both translational and rotational symmetries [1]. Late
 r\, these broken symmetries were turned out to be a characteristic at ener
 gies of the inhomogeneous pseudogap excitations [2].\nHere we apply these 
 mapping techniques to insulating Ca2-xNaxCuO2Cl2 (x = 0.06\, 0.08) to eluc
 idate evolution of broken symmetries with hole doping. We find that the br
 oken symmetry patterns in the superconducting samples appear in virtually 
 identical form in the insulating samples as well. However\, density of suc
 h patterns is smaller in the insulating samples\, and areas preserving the
  symmetry of crystalline lattice are found in between. Moreover\, spectra 
 in the former patterns are V-shaped pseudogap as observed in the underdope
 d superconducting samples\, while those in the latter areas are U-shaped i
 nsulating ones. These results indicate that hole doping into the Mott insu
 lating state causes the local broken symmetries with the pseudogap.\n\n[1]
  Y. Kohsaka et al.\, Science 315\, 1380 (2007).\n[2] Y. Kohsaka et al.\, N
 ature 454\, 1072 (2008).
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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