Sondheimer oscillations as a probe of non-ohmic flow in WP2 crystals

As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm’s law. Depending on the length scales of momentum conserving (lMC) and relaxing (lMR) electron scattering, and the device size (d), current flows may shift from ohmic to ballistic to hydrodynamic regimes. So far, an in situ methodology to obtain these parameters within a micro/nanodevice is critically lacking. In this context, we exploit Sondheimer oscillations, semi-classical magnetoresistance oscillations due to helical electronic motion, as a method to obtain lMR even when lMR ≫ d. We extract lMR from the Sondheimer amplitude in WP2, at temperatures up to T ~ 40 K, a range most relevant for hydrodynamic transport phenomena. Our data on μm-sized devices are in excellent agreement with experimental reports of the bulk lMR and confirm that WP2 can be microfabricated without degradation. These results conclusively establish Sondheimer oscillations as a quantitative probe of lMR in micro-devices.

Full-dimensional quantum stereodynamics of the non-adiabatic quenching of OH(A2Σ+) by H2

The Born–Oppenheimer approximation, assuming separable nuclear and electronic motion, is widely adopted for characterizing chemical reactions in a single electronic state. However, the breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry, and a detailed understanding of the non-adiabatic dynamics is still incomplete. Here we investigate the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 molecules using full-dimensional quantum dynamics calculations for zero total nuclear angular momentum using a high-quality diabatic-potential-energy matrix. Good agreement with experimental observations is found for the OH(X2Π) ro-vibrational distribution, and the non-adiabatic dynamics are shown to be controlled by stereodynamics, namely the relative orientation of the two reactants. The uncovering of a major (in)elastic channel, neglected in a previous analysis but confirmed by a recent experiment, resolves a long-standing experiment–theory disagreement concerning the branching ratio of the two electronic quenching channels.

Controlling Quantum Wave Packet of Electronic Motion on Field-Dressed Coulomb Potential of H2+ by Carrier-Envelope Phase-Dependent Strong Field Laser Pulses

Solving numerically a non-Born-Oppenheimer time-dependent Schrödinger equation to study the dissociative-ionization of H subjected to strong field six-cycle laser pulses (I = 4 × 10 W/cm, λ = 800 nm) leads to newly ultrafast images of electron dynamics in H. The electron distribution in H oscillates symmetrically with laser cycle with θ + π periodicity and gets trapped between two protons for about 8 fs by a Coulomb potential well. Nonetheless, this electron symmetrical distribution breaks up for the H internuclear separation larger than 9 a.u. in the field-free region at a time duration of 24 fs as a result of the distortion of Coulomb potential where the ejected electron preferentially localizes in one of the double-well potential separated by the inner Coulomb potential barrier. Moreover, controlling laser carrier-envelope phase θ enables one to generate the highest total asymmetry A of 0.75 and -0.75 at 10 and 190, respectively, associated with the electron preferential directionality being ionized to the left or the right paths along the H molecular axis. Thus the laser-controlled electron slightly reorganizes its position accordingly to track the shift in the position of the protons despite much heavier the proton’s mass.

A Conceptual Model for Joint Graphic Representation of Mechatronic Systems with Servomechanisms

This article deals with the problem of joint representation of mechanical and motion control information of machines with servo axes. A new conceptual model is proposed for the graphical representation of industrial mechatronic systems covering the minimum information requirements from both mechanical and motion automation points of view. The model also takes into account new electronic motion control concepts such as virtual axes and temporary electronic coordination relationships between axes (e-gears). The objective is to support more integrated and collaborative work between mechanical designers and automation developers when implementing complex machines and industrial mechatronic systems. Schemes graphically representing the relevant common information are obtained from the information model, which may simplify the exchange of information between the mechanical and the motion control fields, not only at conceptualization and design stages, but also throughout the rest of the implementation process of industrial mechatronic systems.

Sondheimer oscillations as a probe of non-ohmic flow in type-II Weyl semimetal WP2

As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm’s law. Depending on the length scales of momentum conserving (lMC) and relaxing (lMR) electron scattering, and the device size (d), current flows may shift from ohmic to ballistic to hydrodynamic regimes and more exotic mixtures thereof. So far, an in situ, in-operando methodology to obtain these parameters self-consistently within a micro/nanodevice, and thereby identify its conduction regime, is critically lacking. In this context, we exploit Sondheimer oscillations, semi-classical magnetoresistance oscillations due to helical electronic motion, as a method to obtain lMR in micro-devices even when lMR>>d. This gives information on the bulk lMR complementary to quantum oscillations, which are sensitive to all scattering processes. We extract lMR from the Sondheimer amplitude in the topological semi-metal WP2, at elevated temperatures up to T~50 K, in a range most relevant for hydrodynamic transport phenomena. Our data on μm-sized devices are in excellent agreement with experimental reports of the large bulk lMR and thus confirm that WP2 can be microfabricated without degradation. Indeed, the measured scattering rates match well with those of theoretically predicted electron-phonon scattering, thus supporting the notion of strong momentum exchange between electrons and phonons in WP2 at these temperatures. These results conclusively establish Sondheimer oscillations as a quantitative probe of lMR in micro-devices in studying non-ohmic electron flow.

Simultaneous observation of nuclear and electronic dynamics by ultrafast electron diffraction

Simultaneous observation of nuclear and electronic motion is crucial for a complete understanding of molecular dynamics in excited electronic states. It is challenging for a single experiment to independently follow both electronic and nuclear dynamics at the same time. Here we show that ultrafast electron diffraction can be used to simultaneously record both electronic and nuclear dynamics in isolated pyridine molecules, naturally disentangling the two components. Electronic state changes (S1→S0 internal conversion) were reflected by a strong transient signal in small-angle inelastic scattering, and nuclear structural changes (ring puckering) were monitored by large-angle elastic diffraction. Supported by ab initio nonadiabatic molecular dynamics and diffraction simulations, our experiment provides a clear view of the interplay between electronic and nuclear dynamics of the photoexcited pyridine molecule.

DEVELOPMENT OF ELECTRONIC CAM MOTION CONTROL FOR SYNCHRONOUS CUTTING SYSTEM

Before the introduction of electronic motion controls, the traditional mechanical camwas the best approach to be used in applications that perform repetitive operations. Where theunique feature of the cam system is that the master-follower relationship is always repeated.When the electronic motion control system was introduced, the ability to duplicate the functionof the mechanical cam becomes possible by electronic control drives called electronic cams.Limitation of speed, accuracy, and random space are some of the problems faced by mechanicalcam. This study made a prototype of the high-speed rotary synchronous cutting system usingelectronic cam feature of motion controller Yaskawa MP-3000 Series with Sigma-7 servosystem. This study has obtained and analyzed a model of the high-speed rotary cutting system,successfully controlled the rotary cutter motion and proved an alternative cam motion operationwith electronic cam motion control. Performance and precision test for high-speed system needto be improved for the future study.