arXiv subjects

K. P. Sinha

Publications and source records attributed to K. P. Sinha.

9 recordsLinked to original sources

arXiv2009

Spectral selectivity from resonant-coupling in microgap-TPV

Near-field energy coupling between two surfaces may arise from frustrated total-internal-reflectance and from atomic dipole-dipole interaction. Such an exchange of energy, if at resonance, greatly enhances the radiation transfer between an emitter and a photovoltaic converter. Computational modeling of selected, but realizable, emitter and detector structures and materials shows the benefits of both near-field and resonance coupling (e.g., with ~ 100nm gaps). In one sense, this is almost an engineering paper. A strong computational model (based on physically-proven concepts and incorporating known and predicted high-temperature properties of acceptable emitter materials) is used to demonstrate the potential of materials (properly-selected to overcome natural limitations) and of structures (carefully crafted to push the limits of present technology) for breaking barriers of thermal conversion at lower-emitter temperatures (< 1000C).

physics.gen-ph↗

arXiv2009

On the mechanism of high-temperature superconductivity in the iron based pnictides

The recent discovery of superconductivity at moderately high temperature (26 K to 55 K) in doped iron-based pnictides (LnO_{1-x}F_xFeAs, where Ln = La, Ce, Sm, Pr, Nd, etc.), having layered-structure-like cuprates, has triggered renewed challenge towards understanding the pairing mechanism. After reviewing the current findings on these systems, a theoretical model of a combined mechanism is suggested in which the phonon-mediated and distortion-field-mediated pairing processes give the right order of superconducting critical temperature T_c. The distortion-field modes arise from Jahn-Teller or pseudo Jahn-Teller effects due to degenerate or near-degenerate iron 3d_{xz} and 3d_{yz} orbitals.

cond-mat.supr-con↗

arXiv2009

Radiative-field quantum-coupling between closely-spaced surfaces

A quantum-mechanical formulation of energy transfer between closely-spaced surfaces is given. Coupling between the two surfaces arises from the atomic dipole-dipole interaction involving transverse-photon exchange. The exchange of photons at resonance greatly enhances the radiation transfer. The spacing (distance) dependence is derived for the quantum well - quantum well situation. The interaction between two planar quantum wells, separated by a gap is found to be proportional to the 4th power of the wavelength-to-gapwidth ratio and to the radiation tunneling factor for the evanescent waves. Expressions for the net power transfer, in the near-field regime, from hot to cold surface for this case is given and evaluated for representative materials. Computational modeling of selected, but realizable, emitter and detector structures and materials shows the benefits of both near-field and resonance coupling (e.g., with 0.1 micron gaps).

physics.gen-ph↗

arXiv2009

A model for enhanced fusion reaction in a solid matrix of metal deuterides

Our study shows that the cross-section for fusion improves considerably if d-d pairs are located in linear (one-dimensional) chainlets or line defects. Such non-equilibrium defects can exist only in a solid matrix. Further, solids harbor lattice vibrational modes (quanta, phonons) whose longitudinal-optical modes interact strongly with electrons and ions. One such interaction, resulting in potential inversion, causes localization of electron pairs on deuterons. Thus, we have attraction of D+ D- pairs and strong screening of the nuclear repulsion due to these local electron pairs (local charged bosons: acronym, lochons). This attraction and strong coupling permits low-energy deuterons to approach close enough to alter the standard equations used to define nuclear-interaction cross-sections. These altered equations not only predict that low-energy-nuclear reactions (LENR) of D+ D- (and H+ H-) pairs are possible, they predict that they are probable.

physics.gen-ph↗

arXiv2008

Riccion as a Cosmic Cold Dark Matter Candidate and late cosmic acceleration

In the past few years, a possibility is investigated, where curvature itself behaves as a source of dark energy. So, it is natural to think whether curvature can produce dark matter too. It is found that, at classical level, higher-derivative gravity yields curvature inspired particles namely riccions [11]. Here, it is probed whether riccion can be a possible source of dark matter. Further, it is found that the late universe accelerates. Here, it is interesting to see that acceleration is obtained from curvature without using any dark energy source of exotic matter.

hep-th↗

arXiv2007

Lochon Catalyzed D-D Fusion in Deuterated Palladium in the Solid State

Lochons (local charged bosons or local electron pairs) can form on D+ to give D- (bosonic ions) in Palladium Deuteride in the solid state. Such entities will occur at special sites or in linear channel owing to strong electron-phonon interaction or due to potential inversion on metallic electrodes. These lochons can catalyze D- - D+ fusion as a consequence of internal conversion leading to the formation of He-4 plus production of energy (Q=23.8 MeV) which is carried by the alpha particle and the ejected electron-pair. The reaction rate for this fusion process is calculated.

physics.gen-ph↗

arXiv2006

On the Laser Stimulation of Low-Energy Nuclear Reactions in Deuterated Palladium

Models to account for the observed experimental results for low-energy nuclear reactions in palladium-deuteride systems are presented along with calculated results. The crucial idea is a mechanism of improved probability for the needed penetration of the Coulomb barrier for a D-D reaction. This facilitation occurs, in general, with the formation of D^- ions at special frequency modes (e.g. via phonons) and, specifically for the laser-stimulated case, with utilization of enhanced optical potential at a selected interface. Both mechanisms may work individually, or together, to increase the probability of barrier penetration.

cond-mat.other↗

arXiv2006

Quantum-coupling between closely-spaced surfaces via transverse photons

A quantum-mechanical formulation of energy transfer between closely spaced surfaces is given. Coupling between the two surfaces arises from the atomic dipole-dipole interaction involving transverse-photon exchange. The exchange of photons at resonance enhances the radiation transfer. The interaction between two surfaces, separated by a gap, is found to be dependent upon geometric, material, frequency, dipole, and temperature factors, along with a radiation-tunneling factor for the evanescent waves. The derived geometric term has a gap-spacing (distance) dependence that varies inversely as the second power for bulk samples to the inverse fourth power for the quantum well - quantum well case. Expressions for the net power transfer, in the near-field regime, from hot to cold surface for this case is given and evaluated for representative materials.

cond-mat.mtrl-sci↗

arXiv2005

High Temperature Superconductivity In Pd-[H(D)]X System

A theoretical model involving phonon and lochon (local charged boson) mediated pairing of electrons in Pd(H/D)x is suggested to explain the possible observation of superconductivity in the range 51K < Tc < 295K (when x exceeds unity). In the combined mechanism the lochons have transient existence on (H+/D+) resulting in (H-/D-) species. The coupling parameter lambda_1 for lochon induced processes depend linearly on x. The model explains the observation of the enhancement of Tc for x varying from 0.6 to 1.6. While the experimental observations are of great importance, it is desirable that other experimental groups confirm the results.

cond-mat.supr-con↗