Haranath Ghosh

Electron-correlation-induced transverse delocalization and longitudinal confinement in excited states of phenyl-substituted polyacetylenes

Electron-electron interactions in general lead to both ground-state and excited-state confinement. We show, however, that in phenyl-substituted polyacetylenes electron-electron interactions cause enhanced delocalization of quasiparticles in the optically excited state from the backbone polyene chain into the phenyl groups, which in turn leads to enhanced confinement in the chain direction. This cooperative delocalization confinement lowers the energy of the one-photon state and raises the relative energy of the lowest two-photon state. The two-photon state is slightly below the optical state in monophenyl-substituted polyacetylenes, but above the optical state in diphenyl-substituted polyacetylenes, thereby explaining the strong photoluminescence of the latter class of materials. We present a detailed mechanism of the crossover in the energies of the one- and two-photon states in these systems. In addition, we calculate the optical-absorption spectra over a wide wavelength region, and make specific predictions for the polarizations of low- and high-energy transitions that can be tested on oriented samples. Within existing theories of light emission from

TIME-REVERSAL SYMMETRY-BREAKING SUPERCONDUCTIVITY

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Photophysics of phenyl-substituted polyacetylenes, theory

-conjugated polymers, strong photoluminescence should be restricted to materials whose optical gaps are larger than that of trans-polyacetylene. The present work shows that, conceptually at least, it is possible to have light emission from systems with smaller optical gaps.

Theory of excited state absorptions in phenylene-based

We study time-reversal symmetry-breaking superconductivity with

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{\ensuremath{\Delta}}_{k}={\ensuremath{\Delta}}_{{x}^{2}\ensuremath{-}{y}^{2}}{(k)+e}^{i\ensuremath{\theta}}{\ensuremath{\Delta}}_{\ensuremath{\alpha}}(\ensuremath{\alpha}=s

-conjugated polymers

or

Coexistence of band Jahn-Teller distortion and superconductivity in correlated systems

{d}_{\mathrm{xy}})

Interplay of spin density wave and superconductivity with different pairing symmetry

symmetries. It is shown that the behavior of such superconductors could be qualitatively different depending on the minor component

Enhancement of superconducting correlation due to interlayer tunneling

(\ensuremath{\alpha})

Superconductors of mixed order-parameter symmetry in a Zeeman magnetic field

and its phase at lower temperatures. It is argued that such qualitatively different behaviors in thermal as well as in angular dependences could be a source of consequences in transport and Josephson physics. Orthorhombicity is found to be a strong mechanism for the mixed phase (in the case of