78 research outputs found
Barkhausen Noise in a Relaxor Ferroelectric
Barkhausen noise, including both periodic and aperiodic components, is found
in and near the relaxor regime of a familiar relaxor ferroelectric,
PbMgNbO, driven by a periodic electric field. The
temperature dependences of both the amplitude and spectral form show that the
size of the coherent dipole moment changes shrink as the relaxor regime is
entered, contrary to expectations based on some simple models.Comment: 4 pages RevTeX4, 5 figures; submitted to Phys Rev Let
Observation of First-Order Metal-Insulator Transition without Structural Phase Transition in VO_2
An abrupt first-order metal-insulator transition (MIT) without structural
phase transition is first observed by current-voltage measurements and
micro-Raman scattering experiments, when a DC electric field is applied to a
Mott insulator VO_2 based two-terminal device. An abrupt current jump is
measured at a critical electric field. The Raman-shift frequency and the
bandwidth of the most predominant Raman-active A_g mode, excited by the
electric field, do not change through the abrupt MIT, while, they, excited by
temperature, pronouncedly soften and damp (structural MIT), respectively. This
structural MIT is found to occur secondarily.Comment: 4 pages, 4 figure
Bandwidth-controlled Mott transition in I. Optical studies of localized charge excitations
Infrared reflection measurements of the half-filled two-dimensional organic
conductors -(BEDT-TTF)Cu[N(CN)]BrCl were
performed as a function of temperature ( K) and
Br-substitution (, 40%, 73%, 85%, and 90%) in order to study the
metal-insulator transition. We can distinguish absorption processes due to
itinerant and localized charge carriers. The broad mid-infrared absorption has
two contributions: transitions between the two Hubbard bands and intradimer
excitations from the charges localized on the (BEDT-TTF) dimer. Since the
latter couple to intramolecular vibrations of BEDT-TTF, the analysis of both
electronic and vibrational features provides a tool to disentangle these
contributions and to follow their temperature and electronic-correlations
dependence. Calculations based on the cluster model support our interpretation.Comment: 12 pages, 12 figure
Observation of Mott Transition in VO_2 Based Transistors
An abrupt Mott metal-insulator transition (MIT) rather than the continuous
Hubbard MIT near a critical on-site Coulomb energy U/U_c=1 is observed for the
first time in VO_2, a strongly correlated material, by inducing holes of about
0.018% into the conduction band. As a result, a discontinuous jump of the
density of states on the Fermi surface is observed and inhomogeneity inevitably
occurs. The gate effect in fabricated transistors is clear evidence that the
abrupt MIT is induced by the excitation of holes.Comment: 4 pages, 4 figure
The impurity ion off-center behavior induced by a localized vibronic Frenkel exciton in a soft-mode crystal
Charge-Transfer Vibronic Excitons as an Origin of a Müller Phase and of Polar Microdomains in Incipient Perovskite-Like Ferroelectrics*
Origin of the structural local transition in the molecular impurity ion MnO 4 2− in the K3Na(CrO4)2 ferroelastic
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