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.

Infrared spectroscopic study of CuO: Signatures of strong spin-phonon interaction and structural distortion

Abstract: ~Received 24 January 2000; revised manuscript received 26 June 2000; published 2 February 2001! Optical properties of single-crystal monoclinic CuO in the range 70‐6000 cm 21 were studied at temperatures from 7 to 300 K. Normal reflection spectra were obtained from the ~001! and ~010! crystal faces thus giving separate data for the Au and Bu phonon modes excited in the purely transverse way ~TO modes!. Mode parameters, including polarizations of the Bu modes not determined by the crystal symmetry, were extracted by the dispersion analysis of reflectivity curves as a function of temperature. Spectra of all the components of the optical conductivity tensor were obtained using the Kramers-Kronig method recently extended to the case of the low-symmetry crystals. The number of strong phonon modes is in agreement with the factor-group analysis for the crystal structure currently accepted for the CuO. However, several ‘‘extra’’ modes of minor intensity are detected; some of them are observed in the whole studied temperature range, while existence of others becomes evident at low temperatures. Comparison of frequencies of ‘‘extra’’ modes with the available phonon dispersion curves points to possible ‘‘diagonal’’ doubling of the unit cell $a,b,c%!$a1c,b,a-c% and formation of the superlattice. The previously reported softening of the Au mode (;400 cm 21 ) with cooling at TN is found to be ;10% for the TO mode. The mode is very broad at high temperatures and strongly narrows in the antiferromagnetic phase. We attribute this effect to strong resonance coupling of this mode to optical or

Conditional statistics of electron transport in interacting nanoscale conductors

Abstract: There is an intimate connection between the acquisition of information and how this information changes the remaining uncertainty in the system. This trade-off between information and uncertainty plays a central role in the context of detection. Recent advances in the ability to make accurate, on-chip measurements of individual-electron current through a quantum dot1,2,3,4,5,6,7,8 (QD) have been enabled by exploiting the sensitivity of a second current, passing through a nearby quantum point contact (QPC), to the fluctuating charge on the QD4,5,6,7,8. An important characteristic of QPC detectors is their minimal influence on the systems they probe. Here we show that even the operation of an effectively non-invasive QPC detector can statistically alter the system’s behaviour. By observing a particular QPC current, the statistical distribution of the QD conditional current undergoes a substantial change in comparison to that expected for unconditional shot noise9. These results are in almost perfect agreement with a theoretical model we develop to predict the joint current probability distribution and conditional transport statistics of interacting nanoscale systems.

Influence of the crystalline phase on the molecular mobility of PVDF

Abstract: Dielectric relaxation and pyrocurrent of PVDF were studied by thermostimulated current spectroscopy. The transition spectrum of the material was investigated by DSC. Two well-resolved relaxation peaks have been observed in the temperature range [-100-100°C]. The molecular mechanisms of these phenomena have been discussed, based on a comparative study of α-PVDF and β-PVDF. The β relaxation mode is located at -41°C in α-PVDF and is slightly shifted toward higher temperatures in the stretched material. This mode has been ascribed to the dielectric manifestation of the glass transition (T g ) of PVDF. It is comprised of two components corresponding to the free and constrained amorphous phases, respectively, in the order of increasing temperatures