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Bhubaneshwar, India

Pal P.S.,Institute of Phsyics | Rana S.,Institute of Phsyics | Saha A.,Heinrich Heine University Dusseldorf | Jayannavar A.M.,Institute of Phsyics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Work can be extracted from a single bath beyond the limit set by the second law of thermodynamics by performing measurement on the system and utilizing the acquired information. This imposes an upper bound on extracted work and maintains a generalized (i.e., with information) second law. As an example, we studied a Brownian particle confined in a two-dimensional harmonic trap in the presence of a magnetic field, whose position coordinates are measured with finite precision. Two separate cases are investigated in this study: (A) moving the center of the potential and (B) varying the stiffness of the potential. Optimal protocols that extremize the work in a finite-time process are explicitly calculated for these two cases. For case A, we show that even though the optimal protocols depend on magnetic field, surprisingly, extracted work is independent of the field. For case B, both the optimal protocol and the extracted work depend on the magnetic field. However, the presence of a magnetic field always reduces the extraction of work for the latter case. © 2014 American Physical Society. Source

Dash J.K.,Institute of Phsyics | Rath A.,Institute of Phsyics | Juluri R.R.,Institute of Phsyics | Satyam P.V.,Institute of Phsyics
Journal of Physics D: Applied Physics

The morphological evolution and the effect of growth temperature on size, orientation and composition of molecular beam epitaxy grown Ge-Si islands on Si(5512) surfaces have been investigated in the temperature range from room temperature to 800°C. Two modes of substrate heating, i.e. radiative heating (RH) and direct current heating (DH) have been used. The post-growth characterization was carried out ex situ by scanning electron microscopy, cross-sectional transmission electron microscopy and Rutherford backscattering spectrometry. In the RH case, we found spherical island structures at 600°C with a bimodal distribution and upon increasing temperature, the structures got faceted at 700°C. At 800°C thick (122nm) dome-like structures are formed bounded by facets. While in the case of dc heating, after the optimum critical temperature 600°C, well aligned trapezoidal Si 1xGe x structures with a graded composition starts forming along the step edges. Interestingly, these aligned structures have been found only around 600°C, neither at low temperature nor at higher temperatures. © 2012 IOP Publishing Ltd. Source

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