arXiv subjects
Publications and source records attributed to P. Roy.
We construct a displacement operator type nonlinear coherent state and examine some of its properties. In particular it is shown that this nonlinear coherent state exhibits nonclassical properties like squeezing and sub-Poissonian behaviour.
We study the motion of a spin 1/2 particle in a scalar as well as a magnetic field within the framework of supersymmetric quantum mechanics(SUSYQM). We also introduce the concept of shape invariant scalar and magnetic fields and it is shown that the problem admits exact analytical solutions when such fields are considered.
The evolution with doping and temperature of the polaronic absorption in a family of high-T$_c$ superconductors is first followed here across the whole phase diagram. The polaron band softens with increasing doping, is still present in the superconducting phase, and vanishes in the overdoped metallic phase. These results point toward the existence of polaron aggregates at low temperature and may provide an experimental ground for the increasing number of theoretical descriptions of many-polaron systems.
We construct even and odd nonlinear coherent states of a parametric oscillator and examine their nonclassical properties.It has been shown that these superpositions exhibit squeezing and photon antibunching which change with time.
We study one dimensional supersymmetric (SUSY) quantum mechanics of a spin 1/2 particle moving in a rotating magnetic field and scalar potential. We also discuss SUSY breaking and it is shown that SUSY breaking essentially depends on the strength and period of the magnetic field. For a purely rotating magnetic field the eigenvalue problem is solved exactly and two band energy spectrum is found.
Polaronic features similar to those previously observed in the photoinduced spectra of cuprates have been detected in the reflectivity spectra of chemically doped parent compounds of high-critical-temperature superconductors, both $n$-type and $p$-type. In Nd$_2$CuO$_{4-y}$ these features, whose intensities depend both on doping and temperature, include local vibrational modes in the far infrared and a broad band centered at $\sim$ 1000 cm$^{-1}$. The latter band is produced by the overtones of two (or three) local modes and is well described in terms of a small-polaron model, with a binding energy of about 500 cm$^{-1}$. Most of the above infrared features are shown to survive in the metallic phase of Nd$_{2-x}$Ce$_x$Cu0$_{4-y}$, Bi$_2$Sr$_2$CuO$_6$, and YBa$_2$Cu$_3$O$_{7-y}$, where they appear as extra-Drude peaks. The occurrence of polarons is attributed to local modes strongly coupled to carriers, as shown by a comparison with tunneling results.
Within the framework of a dynamical and physically transparent model developed earlier, we study the time evolution of various quark flavours in the baryon-free region in ultrarelativistic heavy ion collisions. We show that even under optimistic conditions, the quark-gluon system fails to achieve chemical equilibrium.