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Katsuya Iwaya

Staff photograph
  • Scanning Tunneling Microscopy (STM)
  • Semiconductor surfaces
 Contact details:
Office: 3P1, Lab: B201
Tel: +44 (0)20 7679 0623 (lab)
Ext: 30623
Fax: +44 (0)20 7679 0595
Email: k.iwayaucl.ac.uk

Research Interest
My general interest is to obtain unprecedented data with extremely high resolution and present new challenges to theorists.

Other activities

  • Tutorial (1st year)
  • Member of The Physical Society of Japan

Biography

  • B. A. in Basic Science, University of Tokyo (1998)
  • M. S. in Basic Science, University of Tokyo (2000)
  • Ph. D. in Basic Science, University of Tokyo (2003)
  • Special Postdoctoral Researcher, Magnetic Materials Laboratory, RIKEN  (2003-2006)
  • Research Fellow, Physics and Astronomy, University College London (2006 – present)

Recent Publications

  • K. Iwaya, S. Satow, T. Hanaguri, N. Shannon, Y. Yoshida, S. I. Ikeda, J. P. He, Y. Kaneko, T. Yamada, H. Takagi, Local Tunneling Spectroscopy across a Metamagnetic Critical Point in the Bilayer Ruthenate Sr3Ru2O7, Physical Review Letters. 99, 057208 (2007) [PDF file]

The local spectroscopic signatures of metamagnetic criticality in Sr3Ru2O7, were explored using STM. A pronounced magnetic field dependence was found across the metamagnetic critical point in the local density of states around Fermi energy. In addition, a c(2x2) superstructure was observed over several tens of meV, accompanied by a pseudogap structure in the tunneling spectrum. This result represents a new electronic ordering at the surface in the absence of any measurable surface reconstruction.

  • K. Iwaya, Y. Kohsaka, S. Satow, T. Hanaguri, S. Miyasaka, H. Takagi, Evolution of local electronic states from a metal to a correlated insulator in NiS2-xSex solid-solution. Physical Review B 70, 161103 (2004). [PDF file]

The evolution of local electronic states in NiS2-xSex pyrite across a bandwidth-controlled metal-insulator transition (MIT) was explored by STM. In marked contrast to MIT’s control by doping, the local electronic states are found to be spatially less inhomogeneous even in the vicinity of the MIT.

  • Y. Kohsaka, K. Iwaya, S. Satow, T. Hanaguri, K. Kitazawa, M. Azuma, M. Takano, H. Takagi,Imaging nano-scale electronic inhomogeneity in the lightly doped Mott insulator Ca2-xNaxCuO2Cl2, Physical Review Letters 93, 097004 (2004). [PDF file]

The spatial variation of electronic states was imaged in the lightly doped Mott insulator Ca2-xNaxCuO2Cl2 using STM. We observed nanoscale domains with a high local density of states within an insulating background. Such spatially inhomogeneous electronic states are inherent to slightly doped Mott insulators, and play an important role for the insulator to metal transition.

Research
(Top-left) Topographic image of a pair of Bi dopants in the Si(001) surface at sample-bias-voltage Vs = -2 V.
(Colour) The local density of states at several different energies. Negative (positive) bias-voltages indicate the filled (empty) state energies of the sample from Fermi energy.