Professor D.N. Basov
Department of Physics
University of California, San Diego
Abstract:
One common attribute of several classes of
correlated
electron systems is that the onset of conducting state in these systems
typically occurs in the regime of nano-scale phase separation of chemical,
and/or electronic/magnetic origin. These intrinsic non-uniformities have
been
systematically documented using scanning probe and scattering
techniques.
However, the dynamical properties of multiple electronic phases coexisting
in
macroscopic heterogeneous samples remain unexplored because methods
appropriate
to study dynamics (transport, infrared/optical and many other
spectroscopies)
lack needed spatial resolution. To circumvent this fundamental limitation,
we
applied a new technique: scanning near field infrared microscopy to
investigate
the transition from a correlated insulator to a correlated metal driven by
temperature in vanadium dioxide (VO2) at length scales
down to 10 nano-meter.
In combination with more conventional far field infrared ellipsometry these
studies
uncover spectroscopic signatures of the Mott transition including divergent
effective mass and electronic pseudogap. These findings may help
to settle decades long debate on the respective
roles played by the lattice and by the electron-electron correlations in the
insulator-to-metal transition of VO2. /Science
318, 1750 (2007)/.