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.

Amorphous to crystalline transformation of fe80b20

Abstract: The transformation from the as-quenched amorphous to the crystalline state of ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ was followed isothermally at relatively low temperatures (580 to 630 K) with M\"ossbauer-effect spectroscopy (MES). Both the Allied Chemical Metglas 2605 ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ and twin-roller quenched (RQ) ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ were studied. Before the onset of crystallization the M\"ossbauer recoil-free fraction of the $^{57}\mathrm{Fe}$ nuclei was constant but it increased by about 15% during crystallization. This implies that on the average the Fe atoms are more firmly bound in the crystalline than in the amorphous state. From a combination of MES, x-ray diffraction, and optical microscopy it was found that (a) the MG 2605 ribbons are rather inhomogeneous in the sense that 10% to 15% of the ribbon cross section is considerably more resistant to crystallization than the remaining part, (b) no such inhomogeneity is present in the RQ ribbons, (c) the crystallization takes place by the eutectic type of reaction, the crystallization products are $\ensuremath{\alpha}$-Fe and the (metastable) tetragonal ${\mathrm{Fe}}_{3}$B compound, and (d) a quantitative analysis of the kinetics of the transformation suggests that crystallization occurs only by the growth of (crystalline) nuclei which are already present in the as-quenched amorphous material.

Irreversibility on the Level of Single-Electron Tunneling

Abstract: We present a low-temperature experimental test of the fluctuation theorem for electron transport through a double quantum dot The rare entropy-consuming system trajectories are detected in the form of single charges flowing against the source-drain bias by using time-resolved charge detection with a quantum point contact We find that these trajectories appear with a frequency that agrees with the theoretical predictions even under strong nonequilibrium conditions, when the finite bandwidth of the charge detection is taken into account

Study of cooperative relaxation modes in complex systems by thermally stimulated current spectroscopy

Abstract: Cooperative relaxation modes associated with transitions of various systems have been experimentally resolved into elementary processes characterized by activation enthalpies and entropies following a compensation law. Two transitions with no kinetic effect-solid-solid transition and Curie transition have been studied. In both cases, the corresponding dielectric relaxations are characterized by a compensation phenomenon with transition temperature as the compensation temperature. Dielectric relaxations liberated at the glass transition, T g , have also been studied. They are also associated with a compensation law but, in that case, the compensation temperatures T g + 10/30°. This lag has been attributed to the kinetic character of T g . Note that it is lower in amorphous polymers than in semicrystalline polymers. The distribution function of activation parameters is broader in amorphous polymers than in semicrystalline ones.

Carbondioxide Gating in Silk Cocoon

Abstract: Silk is the generic name given to the fibrous proteins spun by a number of arthropods. During metamorphosis, the larva of the silk producing arthropods excrete silk-fiber from its mouth and spun it around the body to form a protective structure called cocoon. An adult moth emerges out from the cocoon after the dormant phase (pupal phase) varying from 2 weeks to 9 months. It is intriguing how CO2/O2 and ambient temperature are regulated inside the cocoon during the development of the pupa. Here we show that the cocoon membrane is asymmetric, it allows preferential gating of CO2 from inside to outside and it regulates a physiological temperature inside the cocoon irrespective of the surrounding environment temperature. We demonstrate that under simulating CO2 rich external environment, the CO2 does not diffuse inside the cocoon. Whereas, when CO2 was injected inside the cocoon, it diffuses out in 20 s, indicating gating of CO2 from inside to outside the membrane. Removal of the calcium oxalate hydrate crystals which are naturally present on the outer surface of the cocoon affected the complete blockade of CO2 flow from outside to inside suggesting its role to trap most of the CO2 as hydrogen bonded bicarbonate on the surface. The weaved silk of the cocoon worked as the second barrier to prevent residual CO2 passage. Furthermore, we show that under two extreme natural temperature regime of 5 and 50 °C, a temperature of 25 and 34 °C respectively were maintained inside the cocoons. Our results demonstrate, how CO2 gating and thermoregulation helps in maintaining an ambient atmosphere inside the cocoon for the growth of pupa. Such natural architectural control of gas and temperature regulation could be helpful in developing energy saving structures and gas filters.