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Manufacturing firms are embracing new technologies in the fourth industrial revolution. Firms are adopting various digital technologies to become smart and intelligent system. One such technology used widely in manufacturing sector is cyber physical system (CPS). A CPS incorporates a wide range of trans-disciplinary approaches, comprising computer science, cybernetic enhancements theory, design and process science, mechanical engineering and mechatronics, and manufacturing systems. CPS ensures proper connectivity and interaction of physical entities with the online system. Many manufacturing firms are facing challenges in adopting CPS such as low skills to adopt CPS, risk of cyber attach and many more. In this regard, this article presents a review on the concept of CPS along with its adoption challenges. Various challenges arise in adoption of CPS have been discussed in detailed. Further, drivers associated with adoption of CPS technology in manufacturing were also discussed. The drivers such as Legislation and Standardization, Management Strategy and Skilled human resources are observed as significant one for the adoption of CPS in manufacturing systems. The present study will help industrial experts to have clear understanding about the obstacles in adoption of CPS practices in manufacturing sector. [ABSTRACT FROM AUTHOR]

A strong negative magnetoresistance is observed in a high-mobility two-dimensional electron gas in a GaAs/Al0.3Ga0.7As quantum well. We discuss that the negative magnetoresistance consists of a small peak induced by a combination of two types of disorder and a huge magnetoresistance explained by the interaction correction to the conductivity for mixed disorder. [ABSTRACT FROM AUTHOR]

We report on a photoconductive gain in semiconductor quantum wires which are lithographically defined in an AlGaAs/GaAs quantum well via a shallow-etch technique. The effect allows resolving the one-dimensional subbands of the quantum wires as maxima in the photoresponse across the quantum wires. We interpret the results by optically induced holes in the valence band of the quantum well which shift the one-dimensional subbands of the quantum wire. Here we demonstrate that the effect persists up to a temperature of about 17 Kelvin. [ABSTRACT FROM AUTHOR]

The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtained Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region. [ABSTRACT FROM AUTHOR]

Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots. Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of more than 70 ns are extracted from the measured data. [ABSTRACT FROM AUTHOR]

High-mobility two-dimensional electron systems may be one of the bases of future spintronic devices, where the spin states of ballistic electrons could be manipulated via external gate voltages and the resulting spin-orbit fields. Therefore, the knowledge of spin dynamics in such systems is of technical interest and offers on the other side an exciting view on the underlying physics. Here, we present time-resolved Faraday rotation measurements in a high-mobility two-dimensional electron system in a GaAs/AlGaAs quantum well structure grown along the [001] direction. Even without applied external magnetic fields the optically generated spin ensemble shows a coherent precession about the effective spin-orbit field. If a nonquantizing magnetic field is applied normal to the sample plane, the effective spin-orbit fields are rotated by the cyclotron motion of the electrons. This rotation leads to fast oscillations in the spin polarization about a nonzero value and an strong increase of the spin dephasing times. The measurement data is in excellent agreement with a model based on a kinetic equation approach. [ABSTRACT FROM AUTHOR]

With the recent discovery of very long hole spin decoherence times in GaAs/AlGaAs heterostructures of more than 70 ns in two-dimensional hole systems, using the hole spin as a viable alternative to electron spins in spintronic applications seems possible. Furthermore, as the hyperfine interaction with the nuclear spins is likely to be the limiting factor for electron spin lifetimes in zero dimensions, holes with their suppressed Fermi contact hyperfine interaction due to their p-like nature should be able to show even longer lifetimes than electrons. For spintronic applications, electric-field control of hole spin dynamics is desirable. Here, we report on time-resolved Kerr rotation and resonant spin amplification measurements on a two-dimensional hole system in a p-doped GaAs/AlGaAs heterostructure. Via a semitransparent gate, we tune the charge density within the sample. We are able to observe a change in the hole g factor, as well as in the hole spin dephasing time at high magnetic fields. [ABSTRACT FROM AUTHOR]

GaMnAs is a highly interesting material system for future spintronic devices. We present a study of nonmagnetic GaAs quantum wells (QW) embedded in AlGaAs barriers, close to a ferromagnetic GaMnAs layer. The samples were grown on semi-insulating GaAs(001) and contain two QWs, where one QW is close to the GaMnAs layer and the other one is farther away (120 nm), and serves as a reference. We studied the influence of the barrier material, e.g. a short-period AlAs/GaAs superlattice. The photoluminescence (PL) of the upper QWs, close to the GaMnAs layer, show a significant broadening. Additionally, time-resolved Faraday rotation (TRFR) reveals that the spin lifetime in the upper QW is up to 30 times longer than that in the lower QW. We attribute these observations to backdiffusion of Mn into the QW during and after growth. Both, the PL and the TRFR, are highly sensitive to small quantities (below 0.05 %) of Mn and allow us to study the efficiency of barrier layers in suppressing Mn diffusion. [ABSTRACT FROM AUTHOR]

The spin dynamics in [001]-grown two-dimensional electron systems (2DES) at low temperatures are governed by the effective spin-orbit fields, which lead to dephasing via the D’yakonov-Perel mechanism. If both the Rashba and the Dresselhaus spin-orbit fields are present and of the same order, their interference causes a large anisotropy of the spin dephasing times for spin orientation along different in-plane directions. This may be observed in time-resolved Faraday rotation measurements using in-plane magnetic fields. The dephasing anisotropy is strongly reduced for increasing carrier density by the increasing importance of the kubic Dresselhaus term. [ABSTRACT FROM AUTHOR]

We present a study of nonmagnetic GaAs quantum wells (QWs) embedded in AlGaAs barriers close to a Ga(Mn)As layer. The photoluminescence (PL) spectra of QWs close (3 – 10 nm) to the Ga(Mn)As layer show a pronounced broadening and quenching of the PL. This may be due to diffusion of Mn ions into the QW during growth. Employing time-resolved Faraday rotation measurements, we observe that the spin lifetime in the QW, separated by 10 nm from the Ga(Mn)As layer, is increased by a factor of 3, as compared to a control well, at a distance of 122 nm. However, in the measured g factors we see no influence of the Mn. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]