Browsing Physics by Author "Masale, M."
Now showing items 1-6 of 6
-
Masale, M. (Elsevier Science Ltd. www.elsevier.com/locate/physc, August 15, 2002)[more][less]
Abstract: The azimuthal surface nucleation field of an infinitely long type II superconducting cylindrical filament is calculated from the linearized Ginzburg-Landau equation for the order parameter. A current is thought to be passed along the axis of the filament which induces a magnetic field in the azimuthal direction. On increasing the current, the field increases to a value whereby a phase transition from the superconducting to the normal state occurs. The magnetic field lines are parallel to the surface of the cylindrical filament so that the required critical field is Hc3; the parallel surface nucleation field of a type II superconductor. The systems considered are a solid cylinder; free-standing and in a metallic matrix; and a very thin-walled hollow cylinder. The full numerical analysis is carried out only for a solid cylinder. In the case of a thin-walled cylindrical shell, the quantitative description of the superconducting- normal phase is given in terms of the limiting form of the temperature for small fields. URI: http://hdl.handle.net/10311/196 Files in this item: 2
license.txt (1.998Kb) -
Masale, M. (Elsevier Science Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/622948/description#description, NaN, 2008)[more][less]
Abstract: A calculation is presented on the scattering rates of electrons via the bulk spectrum of longitudinal optical phonons near a current-carrying core of radius R employing the Frohlich interaction Hamiltonian. The electrons are mainly confined near the core by an electric potential and are also under the influence of the current-induced spatially inhomogeneous static azimuthal magnetic field. The external magnetic field lifts the double degeneracy of the non-zero electron's axial wave number (kz ) states, while that of the nonzero azimuthal quantum number (m) states is preserved. In fact, the kz < 0 electron's energy subbands are found to be characterized by minima in their variations with the field. The intrasubband scattering rates show a remarkable behavior in their variations with the field. First, for weak electric potential of the nanosystem, these exhibit a strong, nonetheless inharmonic, oscillatory behavior in their variations with the field. The oscillations are, however, smoothed out as the strength of the electrical potential is increased, commencing at lower values of the field, within the same range of values of the field used. Second, for the same strength of the electric potential, there arise phase variations of the scattering rates in their variations with the field, resulting from the variation in the electron's axial wave number. URI: http://hdl.handle.net/10311/232 Files in this item: 2
license.txt (1.998Kb)Masale_SM_2008.pdf (1.267Mb) -
Masale, M. (Elsevier Science Ltd. http://www.elsevier.com/locate/physb, NaN, 2004)[more][less]
Abstract: The energy spectrum of an electron confined near a current-carrying core is obtained as a function of the azimuthal applied magnetic field within the effective-mass approximation. The double degeneracy of the non-zero electron's axial wave number (kz) states is lifted by the current-induced magnetic field while that of the non-zero azimuthal quantum number (m) states is preserved. A further analysis is the evaluations of the oscillator strengths for optical transitions involving the lowest-order pair of the electron's energy subbands within the dipole approximation. The radiation field is taken as that of elliptically polarized light incident along the core axis. In this polarization and within the dipole approximation, the allowed transitions are only those governed by the following specific selection rules. The azimuthal quantum numbers of the initial and final states must differ by unity while the electron's axial wave number is conserved. The azimuthal magnetic field is also found to lift the multiple degeneracies of the kz=0 interaction integrals as well as those of the oscillator strengths for optical transitions. URI: http://hdl.handle.net/10311/244 Files in this item: 2
license.txt (1.998Kb)Masale_PB_2004.pdf (1.197Mb) -
Masale, M. (Elsevier Science Ltd. www.elsevier.com/locate/physb, February NaN, 2002)[more][less]
Abstract: The experimental techniques of attenuated total reflection and grating-coupling were originally employed separately as probes for surface polaritons. However, as far back as the mid-1970s, some value was found in actually combining them into a single tool for probing elementary surface excitations. In this article, the theory of the two methods combined into one probe for surface polaritons is presented. The main results of the calculations, here, are the firstorder diffuse reflectivities, which arise due to the presence of a classical grating. For the ease of presentation, only a semi-infinite specimen is considered and the grating is thought to be deposited only on one interface. The discussion highlights the advantages the combined technique has over either of the two methods when each is employed on its own. URI: http://hdl.handle.net/10311/195 Files in this item: 2
license.txt (1.998Kb) -
Masale, M. (Elsevier Science Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/505712/description#description, NaN, 2003)[more][less]
Abstract: The experimental techniques of attenuated total reflection (ATR) and grating coupling were originally employed separately as probes for polaritons. The combined technique of these methods into a single probe is a very versatile tool for probing elementary surface excitations. A theoretical investigation of this single probe for surface polaritons, ATRgrating coupling, is undertaken. The emphasis is on the calculations of first-order diffuse reflectivities, which arise due to the presence of a classical grating. More specifically, the ATR set-up in the Otto configuration is considered and for ease of presentation of the results, a classical grating is thought to be deposited on only one interface of a surface-active thin-film specimen. The discussion highlights the advantages the combined technique has over either of the two methods when each is employed on its own. URI: http://hdl.handle.net/10311/233 Files in this item: 2
license.txt (1.998Kb) -
Masale, M. (Elsevier Science Ltd. www.elsevier.com/locate/physc, January NaN, 2003)[more][less]
Abstract: The problem of a type II superconducting disk in a spatially inhomogeneous magnetic field is considered. The aim of the investigations undertaken here is to evaluate the effects of the spatial inhomogeneity of the parallel component of the applied magnetic field on the nature of the superconducting nucleation of a short cylinder. Full numerical solutions of the linearized Ginzburg-Landau equation for the order parameter, taking into account only the parallel component of the field, are presented in the case of a solid disk;free-standing and in a metallic matrix. In the case of a mesoscopic system, only the limiting form of the critical temperature is obtained. The temperature-field (e-f) curves are characterized by flux-entry points at each of which the azimuthal quantum number decreases by unity. The quasi-period of the flux-entry points increases in f with the increasing strength of the spatial inhomogeneity of the applied field. The increased effect of coating the superconductor with a suitable normal metal leads to the well known suppression of the critical temperature as well as smoothing out of flux entries. It is predicted that the wiping out of surface nucleation is effected with relative ease when the applied magnetic field is uniform than when it posseses a degree of spatial inhomogeneity. URI: http://hdl.handle.net/10311/197 Files in this item: 2
license.txt (1.998Kb)
Now showing items 1-6 of 6