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.

Gate-Defined One-Dimensional Channel and Broken Symmetry States in MoS2 van der Waals Heterostructures.

Abstract: We have realized encapsulated trilayer MoS2 devices with gated graphene contacts. In the bulk, we observe an electron mobility as high as 7000 cm2/(V s) at a density of 3 × 1012 cm–2 at a temperature of 1.9 K. Shubnikov–de Haas oscillations start at magnetic fields as low as 0.9 T. The observed 3-fold Landau level degeneracy can be understood based on the valley Zeeman effect. Negatively biased split gate electrodes allow us to form a channel that can be completely pinched off for sufficiently large gate voltages. The measured conductance displays plateau-like features.

Magnetoresistance of atomic-size contacts realized with mechanically controllable break junctions

Abstract: We present a comprehensive study of the conductance behavior of atomic-size contacts made of ferromagnetic metals (Co) or noble metals (Au) with ferromagnetic electrodes (Co). In order to separate the influence of the large electrodes from the influence of the contacts themselves, we used different sample geometries. These include combinations of nonmagnetic electrodes connected to magnetic bridges and vice versa as well as different orientations of the magnetic field. The magnetoresistance (MR) curves show very rich behavior with strong MR ratios (MRR). In all geometries the MRR values are of comparable size, reaching up to a few thousand percent in the tunneling regime. We study the possible influence of the micromagnetic order of the domains in the vicinity of the contact as well as ballistic MR, giant MR, tunnel MR, atomically enhanced anisotropic MR (AAMR), and magnetostriction. We conclude that AAMR is the most important origin for the MR at high magnetic fields $(|B|g2\text{ }\text{T})$, while magnetostriction, tunnel MR, and giant MR govern the low-field regime $(|B|l2\text{ }\text{T})$.

Study of Structural and Electrical Properties of Conventional Furnace and Microwave-Sintered BaZr0.10Ti0.90O3 Ceramics

Abstract: Structural, dielectric, piezoelectric, and ferroelectric properties of Zirconium-doped barium titanate (BaZr0.10Ti0.90O3) ceramics prepared by microwave (MWS) and conventional (CS) sintering process are compared. X-ray diffraction and Raman spectroscopy indicate clearly the structural changes and confirm the effective diffusion of zirconium with the MWS technique to form BZT. Scanning electron microscopy reveals a fine grain, and a dense microstructure in the MWS ceramics processed under 4 h of cycle time (including heating, cooling, and holding time) in comparison with CS requiring 22 h. At room temperature the microwave sintered samples exhibit improved electrical properties exhibiting higher resistivity, higher dielectric constant, a lower dielectric loss, and a reduced dependence on frequency. Impedance and electric modulus spectroscopy analysis in the frequency range (40 Hz–1 MHz) and high-temperature range (573–873 K) suggests two relaxation processes attributed to bulk and grain boundary effects in the impedance plots for the both MWS and CS ceramics. The microwave-sintered BZT ceramics are found to be more attractive for room temperature device applications with improved properties, however, at higher temperatures they tend to degrade in comparison with the CS ceramics.

Theory of Laplacian fractals: diffusion limited aggregation and dielectric breakdown model

Abstract: We describe a new theoretical approach that clarifies the origin of fractal structures in irreversible growth models based on the Laplace equation and a stochastic field. This new theory provides a systematic method for the calculation of the fractal dimension D and of the multifractal spectrum of the growth probability (ƒ(α)). A detailed application to the dielectric breakdown model and diffusion limited aggregation in two dimensions is presented. Our approach exploits the scale invariance of the Laplace equation that implies that the structure is self-similar both under growth and scale transformation. This allows one to introduce a Fixed Scale Transformation (instead of coarse graining as in the renormalization group theory) that defines a functional equation for the fixed point of the distribution of basic diagrams used in the coarse graining process. For the calculation of the matrix elements of this transformation one has to consider an infinite, but rapidly convergent, number of processes that occurs outside a considered diagram.