180 research outputs found
Electrically modulated photoluminescence in ferroelectric liquid crystal
Electrical modulation and switching of photoluminescence (PL) have been
demonstrated in pure deformed helix ferroelectric liquid crystal (DHFLC)
material. The PL intensity increases and peak position shifts towards lower
wavelength above a threshold voltage which continues up to a saturation
voltage. This is attributed to the helix unwinding phenomenon in the DHFLC on
the application of an electric field. Moreover, the PL intensity could be
switched between high intensity (field-on) and low intensity (field-off)
positions. These studies would add a new dimension to ferroelectric liquid
crystal's application in the area of optical devices.Comment: 4 figure
Au9+ swift heavy ion irradiation of Zn[CS(NH2)2]3SO4 crystal: Crystalline perfection and optical properties
The single crystal of tris(thiourea)zinc sulphate (Zn[CS(NH2)2]3SO4) was
irradiated by 150 MeV Au9+ swift heavy ions and analyzed in comparison with
pure crystal for crystalline perfection and optical properties. The Fourier
transform infrared and x-ray powder diffraction inferred that swift ions lead
the disordering and breaking of molecular bonds in lattice without formation of
new structural phases. High resolution X-ray diffraction (HRXRD) revealed the
abundance of point defects, and formation of mosaics and low angle grain
boundaries in the irradiated region of crystal. The swift ion irradiation found
to affect the lattice vibrational modes and functional groups significantly.
The defects induced by heavy ions act as the color centers and resulted in
enhance of photoluminescence emission intensity. The optical transparency and
band gap found to be decreased.Comment: 7 page
Coexistence of Band Jahn Teller Distortion and superconductivity in correlated systems
The co-existence of band Jahn-Teller (BJT) effect with superconductivity (SC)
is studied for correlated systems, with orbitally degenerate bands using a
simple model. The Hubbard model for a doubly degenerate orbital with the
on-site intraorbital Coulomb repulsion treated in the slave boson formalism and
the interorbital Coulomb repulsion treated in the Hartree-Fock mean field
approximation, describes the correlated system. The model further incorporates
the BJT interaction and a pairing term to account for the lattice distortion
and superconductivity respectively. It is found that structural distortion
tends to suppress superconductivity and when SC sets in at low temperatures,
the growth of the lattice distortion is arrested. The phase diagram comprising
of the SC and structural transition temperatures and versus the
dopant concentration reveals that the highest obtainable for an
optimum doping is limited by structural transition. The dependence of the
occupation probabilities of the different bands as well as the density of
states (DOS) in the distorted-superconducting phase, on electron correlation
has been discussed.Comment: RevTex, 4 pages, 4 figuers (postscript files attached) Journal
Reference : Phys. Rev. B (accepted for publication
Comprehensive study on l-Proline Lithium Chloride Monohydrate single crystal: A semiorganic material for nonlinear optical applications
Abstractl-Proline Lithium Chloride Monohydrate single crystal has been successfully synthesized and grown by slow evaporation solution technique. The lattice dimensions have been calculated by single crystal XRD. The presence of strain inside the crystal has been evaluated by powder X-ray diffraction. Its crystalline perfection was found to be good with the full width at half maxima of 29.31arc sec. The crystal quality can be further examined by time resolve photoluminescence spectroscopy. The dielectric constant and dielectric loss have been measured over the frequency range of 10Hz–10kHz. The curve plotted during the measurement suggests that the value of dielectric constant decreases at higher frequency which ensures that the crystal is good candidate for NLO devices. The laser damage threshold measurements have been performed for single and multiple shots which reveal that the tolerance power for the single shot is more as compared to multiple shots. Its third order nonlinearity and thermal parameters have also been assessed for the title compound. The interference patterns obtained from the birefringence studies infer the optical homogeneity and defects in the grown crystals. The density of the single crystal has been calculated by floating technique taking kerosene as a reference
Facile route to produce spherical and highly luminescent Tb3+doped Y2O3nanophosphors
Terbium doped yttrium oxide (Y2O3:Tb3+) nanophosphor has been synthesized via a facial yet modified co-precipitation method. To get maximum luminescence output from Y2O3:Tb3+nanophosphors, surfactants namely, Cetyl trimethylammonium bromide (CTAB) and Trioctylphosphine oxide (TOPO) were added during synthesis. Further, it has been observed that combined addition of surfactant (CTAB�+�TOPO) at the time of synthesis has resulted in nearly spherical morphology of the nanophosphor. Furthermore, these optimized material are observed to have enhanced integrated photoluminescence (PL) intensity of ∼23% as compared to the one synthesized without the addition of any surfactant. The results are further supported by detailed structural and optical studies. Optimum use of surfactants during synthesis shows for the first time that both nano-sized distribution and high crystallinity can be achieved simultaneously which has resulted in bright green emission in Tb3+doped Y2O3nanophosphors. � 201
Time reversal symmetry breaking superconductivity
We study time reversal symmetry breaking superconductivity with ( or )
symmetries. It is shown that the behavior of such superconductors could be {\em
qualitatively} different depending on the minor components () and its
phase at lower temperatures. It is argued that such {\em qualitatively
different} behaviors in thermal as well as in angular dependencies could be a
{\em source} of consequences in transport and Josephson physics.
Orthorhombicity is found to be a strong mechanism for mixed phase (in case of
). We show that due to electron correlation the order parameter is
more like a pure symmetry near optimum doping.Comment: 5 pages, 5 figures (attached), to be published in Physical Review
Valence band and core-level analysis of highly luminescent ZnO nanocrystals for designing ultrafast optical sensors
Highly luminescent ZnO:Na nanocrystals of size ~2 nm were synthesized using a
improved sol-lyophilization process. The surface analysis such as survey scan,
core-level and valence band spectra of ZnO:Na nanocrystals were studied using
x-ray photoelectron spectroscopy (XPS) to establish the presence of Na+ ions.
The observed increase in band gap from 3.30 (bulk) to 4.16 eV (nano), is
attributed to the quantum confinement of the motion of electron and holes in
all three directions. The photoluminescence and decay measurements have
complemented and supported our study to design an efficient and ultrafast
responsive optical sensing device.Comment: 10 Pages, 5 Figure
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