arXiv subjects

I. A. Young

Publications and source records attributed to I. A. Young.

4 recordsLinked to original sources

arXiv2019

Localized bright luminescence of indirect excitons and trions in MoSe$_2$/WSe$_2$ van der Waals heterostructure

Indirect excitons (IX) in semiconductor heterostructures are bosons, which can cool below the temperature of quantum degeneracy and can be effectively controlled by voltage and light. IX quantum Bose gases and IX devices were explored in GaAs heterostructures where an IX range of existence is limited to low temperatures due to low IX binding energies. IXs in van der Waals transition-metal dichalcogenide (TMD) heterostructures are characterized by large binding energies giving the opportunity for exploring excitonic quantum gases and for creating excitonic devices at high temperatures. TMD heterostructures also offer a new platform for studying single-exciton phenomena and few-particle complexes. In this work, we present studies of IXs in MoSe$_2$/WSe$_2$ heterostructures and report on two IX luminescence lines whose energy splitting and temperature dependence identify them as neutral and charged IXs. The experimentally found binding energy of the indirect charged excitons, i.e. indirect trions, is close to the calculated binding energy of 28 meV for negative indirect trions in TMD heterostructures [Deilmann, Thygesen, Nano Lett. 18, 1460 (2018)]. We also report on the realization of IXs with a luminescence linewidth reaching 4~meV at low temperatures. An enhancement of IX luminescence intensity and the narrow linewidth are observed in localized spots.

cond-mat.mes-hall↗

arXiv2019

Convolution Inference via Synchronization of a Coupled CMOS Oscillator Array

Oscillator neural networks (ONN) are a promising hardware option for artificial intelligence. With an abundance of theoretical treatments of ONNs, few experimental implementations exist to date. In contrast to prior publications of only building block functionality, we report a practical experimental demonstration of neural computing using an ONN. The arrays contain 26 CMOS ring oscillators in the GHz range of frequencies tuned by image data and filters. Synchronization of oscillators results in an analog output voltage approximating convolution neural network operation.

cs.ET↗

arXiv2019

A Coupled CMOS Oscillator Array for 8ns and 55pJ Inference in Convolutional Neural Networks

Oscillator neural networks (ONN) based on arrays of 26 CMOS ring oscillators designed and fabricated. ONN are used for inference of dot products with image fragments and kernels necessary for convolutional neural networks. The inputs are encoded as frequency shifts of oscillators using current DACs. Degree of match (DOM) is determined from oscillators synchronization. Measurements demonstrate high correlation of DOM and dot products. Inference requires the time of 8ns and energy of 55pJ.

cs.ET↗

arXiv2019

Exciton gas transport through nano-constrictions

An indirect exciton is a bound state of an electron and a hole in spatially separated layers. Two-dimensional indirect excitons can be created optically in heterostructures containing double quantum wells or atomically thin semiconductors. We study theoretically transmission of such bosonic quasiparticles through nano-constrictions. We show that quantum transport phenomena, e.g., conductance quantization, single-slit diffraction, two-slit interference, and the Talbot effect, are experimentally realizable in systems of indirect excitons. We discuss similarities and differences between these phenomena and their counterparts in electronic devices.

cond-mat.mes-hall↗