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.

Structural, optical and electronic properties of homoepitaxial GaN nanowalls grown on GaN template by laser molecular beam epitaxy

Abstract: We have grown homoepitaxial GaN nanowall networks on GaN template using an ultra-high vacuum laser assisted molecular beam epitaxy system by ablating solid GaN target under a constant rf nitrogen plasma ambient The effect of laser repetition rate in the range of 10 to 30 Hz on the structural properties of the GaN nanostructures has been studied using high resolution X-ray diffraction, field emission scanning electron microscopy and Raman spectroscopy The variation of the laser repetition rate affected the tip width and pore size of the nanowall networks The z-profile Raman spectroscopy measurements revealed the GaN nanowall network retained the same strain present in the GaN template The optical properties of these GaN nanowall networks have been studied using photoluminescence and ultrafast spectroscopy and an enhancement of optical band gap has been observed for the nanowalls having a tip width of 10–15 nm due to the quantum carrier confinement effect at the wall edges The electronic structure of the GaN nanowall networks has been studied using X-ray photoemission spectroscopy and it has been compared to the GaN template The calculated Ga/N ratio is largest (∼2) for the GaN nanowall network grown at 30 Hz Surface band bending decreases for the nanowall network with the lowest tip width The homoepitaxial growth of porous GaN nanowall networks holds promise for the design of nitride based sensor devices

Topologically Nontrivial Valley States in Bilayer Graphene Quantum Point Contacts

Abstract: We present measurements of quantized conductance in electrostatically induced quantum point contacts in bilayer graphene. The application of a perpendicular magnetic field leads to an intricate pattern of lifted and restored degeneracies with increasing field: at zero magnetic field the degeneracy of quantized one-dimensional subbands is four, because of a twofold spin and a twofold valley degeneracy. By switching on the magnetic field, the valley degeneracy is lifted. Because of the Berry curvature, states from different valleys split linearly in magnetic field. In the quantum Hall regime fourfold degenerate conductance plateaus reemerge. During the adiabatic transition to the quantum Hall regime, levels from one valley shift by two in quantum number with respect to the other valley, forming an interweaving pattern that can be reproduced by numerical calculations.

Coulomb Gap in Graphene Nanoribbons

Abstract: We investigate the density- and temperature-dependent conductance of graphene nanoribbons with varying aspect ratio. Transport is dominated by a chain of quantum dots forming spontaneously due to disorder. Depending on ribbon length, electron density, and temperature, single or multiple quantum dots dominate the conductance. Between conductance resonances, cotunneling transport at the lowest temperatures turns into activated transport at higher temperatures. The density-dependent activation energy resembles the Coulomb gap in a quantitative manner. Individual resonances show signatures of multilevel transport in some regimes, and stochastic Coulomb blockade in others.

Formation of a periodic wave structure on the dry surface of a solid by TEA-CO 2 -laser pulses

Abstract: The formation of periodic wave patterns on surfaces of insulators and metals by means of TEA-CO2-laser pulses was observed. The wavelength of the patterns equals that of the laser radiation. The phenomenon is illustrated by samples of quartz glass and copper.