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.

Transmission-grating-photomasked transient spin grating and its application to measurement of electron-spin ambipolar diffusion in (110) GaAs quantum wells

Abstract: A circular dichromatic transient absorption difference spectroscopy of transmission-grating-photomasked transient spin grating is developed and formularized. It is very simple in experimental setup and operation, and has high detection sensitivity. It is applied to measure spin diffusion dynamics and excited electron density dependence of spin ambipolar diffusion coefficient in (110) GaAs quantum wells. It is found that the spin ambipolar diffusion coefficient of (110) and (001) GaAs quantum wells is close to each other, but has an opposite dependence tendency on excited electron density. This spectroscopy is expected to have extensive applicability in the measurement of spin transport.

Effect of gate dielectric thickness on gate leakage in tunnel field effect transistor

Abstract: Gate leakage is one of the important parameter expected to limit the performance of Tunnel FETs. We have simulated the effect of gate dielectric thickness on gate leakage in Tunnel FETs, using two dimensional numerical simulations. It has been observed that gate leakage considerably affects the subthreshold characteristics of TFETs. It was found to be most important component of off-state current and should be considered in future TFET device design. Effects of gate metal workfunction on device characteristics, particularly, gate leakage and origin of reverse tunneling at drain have also been discussed.

Subband densities in quantum wells under in-plane magnetic fields

Abstract: The dependence of the subband densities in a potential well with tunable symmetry on a weak in-plane magnetic field is investigated experimentally by analyzing Shubnikov--de Haas oscillations. We measure a strong carrier redistribution between the subbands, which is explained by individual magnetic-field--dependent density of states in different subbands rather than by the diamagnetic energy shift. The measured carrier redistribution is quantitatively explained considering the in-plane field in second-order perturbation theory.

Bouncing states in quantum dots

Abstract: We observe sequences of asymmetric Coulomb blockade resonances in the conductance of a closed quantum dot. Around a symmetric peak at the center of such a sequence, several asymmetric resonances with a steep flank facing the central peak are found. This effect occurs for an average coupling of the quantum dot states to the leads which is of the order of both their average energy level spacing as well as of the thermal energy. These observations are interpreted in terms of a single state (``bouncing state'') that couples particularly well to the leads. Such a state can influence the line shapes of several neighboring Coulomb blockade resonances.

Electron cascade for distant spin readout.

Abstract: The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes. A cascade can transmit information along a quantum dot array over a distance that extends by far the effect of the direct Coulomb repulsion. We demonstrate that a cascade of electrons can be combined with Pauli spin blockade to read out distant spins and show results with potential for high fidelity using a remote charge sensor in a quadruple quantum dot device. We implement and analyse several operating modes for cascades and analyse their scaling behaviour. We also discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. The high connectivity of such arrays greatly improves the capabilities of quantum dot systems for quantum computation and simulation.