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.

Radiation damage in NaCl. I. Optical-absorption experiments on heavily irradiated samples.

Abstract: Results of optical-absorption experiments on heavily irradiated NaCl single crystals are presented. The dose rates were between 4 and 250 Mrad/h; the doses between 1 and 7 Grad. The irradiation temperatures were in the range of 20--150 \ifmmode^\circ\else\textdegree\fi{}C. Because of the intense optical bands, the thickness of the samples had to be reduced to values between 2 and 100 \ensuremath{\mu}m using a thinning device. With this device we are able to investigate samples containing about 1 mol % Na and ${\mathrm{Cl}}_{2}$. The optical spectra of the samples, irradiated at low temperatures, show intense F, M, R, and N bands. The positions of the optical bands of the electron excess centers are in agreement with the literature. With increasing irradiation temperature, the contribution of these centers to the total amount of radiation damage decreases due to coagulation to colloidal Na particles. The colloid band, however, is much wider than the literature values; in addition, it is located at longer wavelengths. These observations can be explained by assuming that we are dealing with extremely small colloids, showing appreciable quantum size effects.

Measuring the Degeneracy of Discrete Energy Levels Using a GaAs/AlGaAs Quantum Dot.

Abstract: Two new transport measurements in GaAs quantum dots--one addressing spin-related transport, another quantum state degeneracy--use methods that could be adopted in other systems.

Role of linear and cubic terms for drift-induced Dresselhaus spin-orbit splitting in a two-dimensional electron gas

Abstract: The Dresselhaus spin-orbit interaction (SOI) of a series of two-dimensional electron gases hosted in GaAs/AlGaAs and InGaAs/GaAs (001) quantum wells (QWs) is measured by monitoring the precession frequency of the spins as a function of an in-plane electric field. The measured spin-orbit-induced spin splitting is linear in the drift velocity, even in the regime where the cubic Dresselhaus SOI is important. We relate the measured splitting to the Dresselhaus coupling parameter $\ensuremath{\gamma}$, the QW confinement, the Fermi wave number ${k}_{\text{F}}$, and strain effects. From this, $\ensuremath{\gamma}$ is determined quantitatively, including its sign.

EPR of Gd 3 + -metal-ion complexes in Ca F 2 , Ba F 2 , and Sr Cl 2

Abstract: EPR experiments of ${\mathrm{Gd}}^{3+}\ensuremath{-}{M}^{+}$ complexes in Ca${\mathrm{F}}_{2}$, Ba${\mathrm{F}}_{2}$, and Sr${\mathrm{Cl}}_{2}$ crystals are reported. We have studied the effect of the excess negative charge of the metal-ion impurity on the crystal field; also the relaxations of the halide ions neighboring the complex have been investigated. It will be shown that the values of the second-degree crystal-field parameters as determined from the EPR spectra can be explained in terms of an extended-point-charge model. For the calculations of the magnetic parameters we have taken into account second-order effects of odd crystal-field terms which have also been calculated using the point-ion-lattice model. Distortions of the lattice surrounding the ${\mathrm{Gd}}^{3+}\ensuremath{-}{M}^{+}$ complexes are found to have large effects on the magnitude of the second-degree crystal-field parameters. Our experimental results have also been interpreted on the basis of the superposition model in which it is assumed that the crystal-field parameters are determined by the nature and positions of the nearest neighbors of the ${\mathrm{Gd}}^{3+}$ impurity. It will be shown in this paper that for ${\mathrm{Gd}}^{3+}\ensuremath{-}{M}^{+}$ complexes in Ca${\mathrm{F}}_{2}$ the superposition model predicts unrealistically large displacements of the fluorine ions neighboring the ${\mathrm{Gd}}^{3+}$ and ${M}^{+}$ impurity.