Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Dense electronic excitation induced defects in fused silica

Abstract: Investigation of defects created in optical grade fused silica due to 200 MeV silver ion irradiation is reported. Paramagnetically positively charged oxygen vacancies or neutral dangling Si bonds (E' centres), non-bridging oxygen hole centres (NBOHC) and non-paramagnetic defects like B2 bands are observed. The fluence dependent optical and paramagnetic behaviours of these defects are studied using UV–visible absorption spectroscopy, photoluminescence spectroscopy, infrared (IR) absorption and electron paramagnetic resonance. It is observed that generation of E' centres, NBOHC and B2 bands gets saturated beyond a fluence of 1 × 1012 ions cm−2. IR spectra showing saturation in transmission at this fluence also support this observation. At this fluence samples get fully covered with latent tracks containing these defects.

Dynamics of a localized spin excitation close to the spin-helix regime

Abstract: The time evolution of a local spin excitation in a (001)-confined two-dimensional electron gas subjected to Rashba and Dresselhaus spin-orbit interactions of similar strength is investigated theoretically and compared with experimental data. Specifically, the consequences of the finite spatial extension of the initial spin polarization is studied for non-balanced Rashba and Dresselhaus terms and for finite cubic Dresselhaus spin-orbit interaction. We show that the initial out-of-plane spin polarization evolves into a helical spin pattern with a wave number that gradually approaches the value $q_0$ of the persistent spin helix mode. In addition to an exponential decay of the spin polarization that is proportional to both the spin-orbit imbalance and the cubic Dresselhaus term, the finite width $w$ of the spin excitation reduces the spin polarization by a factor that approaches $\exp(-q_0^2 w^2/2)$ at longer times.

Magnetic-field dependence of the gaps in a two-band superconductor: A point-contact study of MgB 2 single crystals

Abstract: We present the results of directional point-contact measurements in ${\mathrm{MgB}}_{2}$ single crystals, in magnetic fields up to 9 T parallel to the c axis. By fitting the conductance curves of our point contacts---showing clear Andreev-reflection features---with a generalized Blonder-Tinkham-Klapwijk model, we extracted the values of the two gaps ${\ensuremath{\Delta}}_{\ensuremath{\sigma}}$ and ${\ensuremath{\Delta}}_{\ensuremath{\pi}}.$ The resulting ${\ensuremath{\Delta}}_{\ensuremath{\sigma}}(B)$ and ${\ensuremath{\Delta}}_{\ensuremath{\pi}}(B)$ curves agree very well with the predictions of the two-band model in dirty limit when the $\ensuremath{\pi}$-band diffusivity is a few times greater than the $\ensuremath{\sigma}$-band one. This result concurs with other experimental and theoretical findings in indicating that, even in the best crystals, the $\ensuremath{\pi}$ band is moderately dirty.

Structure of liquid equiatomic KSn and CsSn.

Abstract: The structure factors of liquid equiatomic KSn and CsSn alloys have been determined by neutron diffraction. A distinct peak at about 1 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$, the first sharp diffraction peak (FSDP), occurs in all measured structure factors. The temperature dependence of the structure has been studied for KSn: apart from the FSDP, whose position shifts toward smaller wave vector and magnitude decreases with increasing temperature, the structure factor remains essentially unaltered. The radial distribution function clearly shows three maxima in the first coordination shell. The simultaneous presence of the FSDP and several maxima in the first coordination shell are indications of formation of polyatomic species in the liquid. Application of two simple structural models, taking into account the presence of structural units, yields reasonable agreement with the measured structure factors.