Narrow Results

By adding a rotating magnetic field in one incoming lead, we calculate the shot noise with different incident states in a 4-lead beam-splitter. The result shows that the shot noise of singlet and triplet states oscillates with the external magnetic field and depends on the symmetric properties of the incident states. Thus, the singlet, entangled triplet, and polarized states can be distinguished by adjusting the magnetic field.

The Rashba spin–orbit coupling (RSOC) effect on the polarization and shot noise properties in a strained WSe₂ multiple barrier structure is studied by transfer-matrix technique. The results indicate that the spin-dependent Fano factor depends on the strain and RSOC strength with oscillatory evolution. Thus, the value of Fano factor with spin rotation can be tuned mechanically and by an external electric field. Also, Fano factor shows high sensitivity to the number of electrostatic barriers in strained WSe₂ multiple barrier structure. Meanwhile, in a strained WSe₂ multiple barrier structure both sign and value of the valley and spin polarizations could be adjusted by tuning both RSOC and strain strength. These findings show that a WSe₂ multiple barrier structure under strain and RSOC can be useful for future spintronics, straintronic and valleytronic devices.

We study shot noise for electron pairs in a 4-lead beam-splitter with each incoming lead driven by a Rashba interaction. The Rashba phases modify the symmetry of the spin part of the wavefunction. Hence, intermediate degrees of bunching and antibunching can be induced.

We study shot noise for entangled electrons in a 4-lead beam-splitter with one incoming lead driven by adiabatically rotating magnetic fields. We propose a setup of an adiabatically rotating magnetic field which is appropriate for an electron beam to transport through. Using the scattering matrix approach, we find that shot noise for the singlet and that for the entangled triplet oscillates between bunching and antibunching due to the influence of the Berry phase. It provides us with a new approach for testing the Berry phase in electron transport on the basis of entanglement.

We investigated the spin-dependent shot noise in aperiodic semiconductor multilayers heterostructures in the presence of the Rashba spin-orbit interaction and an electric field. The results indicate that the shot noise and Fano factor are strongly spin-dependent and can be greatly modulated not only by the external bias voltage and Rashba spin-orbit interaction but also by the thicknesses of block A and B. Our investigations may provide away to design the detection system electronic devices.

In recent years, with the development of mesoscopic physics and nanoelectronics, the research on noise and testing technology of electronic components has been developed. It is well known that noise can characterize the transmission characteristics of carriers in nanoscale electronic components. With the continuous shrinking of the device size, the carrier transport of nanoscale MOSFET devices has been gradually transformed from the traditional drift-diffusion to become the quasi-ballistic or ballistic transport, and its current noise contains granular and thermal noise. The paper by Jeon et al. [The first observation of shot noise characteristics in 10-nm scale MOSFETs, in Proc. 2009 Symp. VLSI Technology (IEEE, Honolulu, 2009), pp. 48–49] presents the variation relation of 20 nm MOSFET current noise with source–drain current and voltage, and its current noise characteristic is between thermal noise and shot noise, so 20 nm MOSFET current noise is shot noise and thermal noise. The paper by Navid et al. [J. Appl. Phys.101 (2007) 124501] shows through simulation that the 60 nm MOSFET current noise is suppressed shot noise and thermal noise. At present, the current noise has seriously affected the basic performance of the device, thus the circuit cannot work normally. Therefore, it is necessary to study the generation mechanism and characteristics of current noise in electronic components so as to suppress device noise, which can not only realize the reduction of device noise, but also play a positive role in the work-efficiency, life-span and reliability of electronic components.

We consider bivalve (oyster) behavior using high frequency valvometry data. These data are obtained in the field in the Arcachon bay, with light-weight electrodes of millimeters size, attached to the molluscs, and linked by flexible wires to an electronic control unit which measures valve activity. The latter are able to move freely and open their valve with an amplitude which is linked to environmental and physiological conditions, in order to filter surrounding waters. We consider here daily data recorded every 0.1 sec for 16 different animals, corresponding to a total of 1 728 000 data points. Valvometry data show important intermittent activity at high frequency, with frequent and sudden "microclosing" events (meaning partial closures), at apparently random times and with random amplitudes. The overall frequency spectrum of valve opening time series show power-law behavior with a slope β = 1.6 ± 0.1. The random succession of closing events with random amplitudes suggests to consider a shot-noise analysis, with two independent stochastic processes representing respectively the times of these discrete shot noise events and their amplitudes. This shows that methods and approaches devoted to extreme values, chaotic dynamics, recurrence time statistics in geosciences and climate studies can also be used to study living organisms and their interactions with complex environments such as their local ecosystem.

In this letter, we will show that the current through the oxide in MOS structures is not always characterized by full shot noise, as it is generally assumed. We will report different noise behaviors associated to different conduction mechanisms through the oxide and we will discuss a case where the noise characterization has been used as a powerful probe of the charge transport mechanism, thus resulting in the discrimination between the several proposed models.

The distinction between "physical" and "equivalent" noise sources in bipolar junction transistors and other semiconductor devices has become blurred in the current engineering textbooks. An unfortunate consequence of this is the emergence in the literature of fictitious noise sources such as the "the collector-current shot noise" and the "base-current shot noise". These are often assigned a physical reality and incorrectly treated as real physical noise sources, independent of circuit topology. Text-books have encouraged successive generations of students in this belief. Non-physical noise sources such as these are convenient and legitimate, even essential, for the effective modeling and simulation of circuit noise. However their naïve use in teaching and research is likely to continue to give rise to fallacious concepts and misleading conclusions. The physical. The physical modeling of the light-emitting diode, the photon transport transistor and the bipolar junction transistor are briefly discussed to illustrate this view.

We apply the quantum trajectory method to current noise in resonant tunneling devices. The results from dynamical simulation are compared with those from unconditional master equation approach. We show that the stochastic Schrödinger equation approach is useful in modeling the dynamical processes in mesoscopic electronic systems.

An ensemble Monte Carlo simulator self-consistently coupled with a Poisson solver is used to study the influence of the density, occupancy and location of electrons traps on the current fluctuations in nondegenerate quasiballistic structures. Transport and noise are found to depend significantly on the density and location of the traps. In particular, the presence of traps increases the noise level as compared with the purely ballistic case. The nonuniformity of the trap occupancy profiles along the active region of the structures affects markedly (specially for low trap densities) the dependence of shot noise on the applied voltage. The location of the traps with respect to the potential minimum appearing in the structures because of the presence of space charge determines their influence on the noise level, fact which can be of help to identify the trap position.

The possibilities of beam intensity noise rejection offered by a narrow-band closed opto-electronic loop system are studied. The noise added to the beam by the acousto-optic modulator used as the actuator is computed. The intensity noise of the in-loop beam can be found below the standard quantum limit but the extracted beam noise is always above this limit. For an input beam with a small excess noise, an increase of the noise can be observed. A simple model of the loop based on the noise transfer functions approach is used for the calculation of the noise power of beam intensities and photocurrents. The behavior of the system and the limitations of noise rejection are analyzed.

The 3D Monte Carlo simulation of an Si dot-based double-tunnel junction shows not only the possibility of shot noise suppression down to the Fano factor of 0.5, but also of super-Poissonian noise. The counting statistics of the tunneling events provides a clear interpretation of the different noise regimes according to the balance between the different tunneling rates involved.

Spectrum S_iD of the white current noise i_D(t) in p–n junction with the ideality factor η of the current–voltage characteristic, which is greater than one, is investigated here. It is shown, that the Van der Ziel relation, S_iD = 2q(I_D + 2I_s), intended for η = 1, is inapplicable if η > 1; here q is the elementary charge, I_D is the current through the junction, and I_s is the saturation current. As the first step, the simplest case is considered, η = 2. That is the main recombination of injected electrons and holes takes place in the middle of the junction depleted region. Such junction may be modeled by two identical junctions with η = 1, which are connected in series. The current noise i_D(t) is determined by noise sources of both junctions. Obtained result is generalized by the use of the Gupta theorem for the thermal noise spectrum in nonlinear resistive systems. The current noise spectrum is found, S_iD = (2q/η) · (I_D + 2I_s). This result is the modification of the Van der Ziel relation extended to η ≥ 1. Experimental proof of the modified relation is made by analysis of the white noise spectrum in Schottky diode with δ-doping (having η = 2.2) in the vicinity of thermodynamical equilibrium.

An analysis and investigation of noises of GaAs tunnel diodes, which abrupt p⁺-n⁺ profile was obtained by using amphoteric nature of silicon, were performed. The main scope of this work was to verify the concepts of the explanation of white noise characteristics on the ground of shot noise and on the ground of the Gupta theorem of thermal noise in resistive elements. The other scope was to investigate the peculiarities of low frequency noise in p⁺-n⁺ junctions formed by using amphoteric silicon nature.

We discuss several aspects of shot noise suppression in mesoscopic cavities, focusing on the so-called “quantum to classical” crossover that can be induced by an increase of the width of the constrictions defining the cavity, an increase in the energy of the injected electrons or the application of a magnetic field. After reviewing the relevant literature, we present some results of our numerical simulations, and point out an alternative explanation of the observed shot noise suppression and the reasons why several statements that can be found in the literature are debatable. Overall, we point out how shot noise behavior in mesoscopic cavities can be explained without any need for classically chaotic dynamics and only on the basis of quantum chaos resulting from diffraction at the constrictions.

When the rate of shot noise is controlled by on–off states we speak of intermittent shot noise. The on–off states lead to alternately occurring clusters of events and intermissions, respectively. We derive the power spectrum of the intermittent shot noise by applying the Wiener-Khinchin theorem. Besides reduced shot noise, we obtain excess noise, which depends on the parameters of the on–off states. We calculate the excess noise for power-law distributed on-states; within the scaling region, the excess noise is excellently approximated by $C/f^b$. The behavior of the slope b and of the amplitude C in dependence of the on–off times is investigated. For large scaling regions, we find a preference for a pure 1/f shape. Finally, we regard the variance of events occurring within a time interval. In the presence of 1/f fluctuations, the variance of counts attains extreme values which are accompanied by an extreme property of slope b.

We study electron transport through molecular chains attached with two nonsuperconducting electrodes by the use of Green's function technique. Here, we do parametric calculations based on the tight-binding model to characterize the electron transport through such bridge systems and see that the transport properties are significantly affected by (a) the length of the molecular chain and (b) the molecule-to-electrode coupling strength. In this context, we also discuss the steady state current fluctuations, so-called shot noise, which is a consequence of the quantization of charge and is not directly available through conductance measurements.

We consider transport through a single-walled carbon nanotube (CNT) in the ballistic regime where weak backscattering at the two contacts gives rise to Fabry-Perot (FP) oscillations in conductance and shot noise. We include the electron-electron interaction and the finite length L of the CNT within the inhomogeneous Tomonaga-Luttinger liquid (TLL) model appropriate for the CNT and treat the non-equilibrium effects due to an applied bias voltage within the Keldysh approach. At low frequencies, the shot noise is S = 2e|I_B|, where e is the elementary charge and I_B is the backscattered current. Interaction effects are apparent via a characteristic power-law and FP-oscillation suppression of I_B at large bias voltage in agreement with our low-frequency shot noise experiments. The extracted TLL parameter g agrees well with theoretical predictions. At frequencies above v_F/gL, with v_F the Fermi velocity, the theoretical impurity noise as a function of bias voltage and frequency shows clear and distinct signatures of the two velocities of collective modes present in the CNT which distinguish spin from charge degrees of freedom (spin-charge separation).

Japan constructed the first ‘compact’ X-ray free-electron laser (XFEL), and started user operation in 2012. This chapter describes the historical development of the compact XFEL concept, the underlying physical principles of XFEL, the details of the accelerator system, the details of the photon beam line, and the scientific applications, followed by a brief comment on the future trend of the XFEL facilities.