1,475 research outputs found
Photocurrent, Rectification, and Magnetic Field Symmetry of Induced Current Through Quantum Dots
We report mesoscopic dc current generation in an open chaotic quantum dot
with ac excitation applied to one of the shape-defining gates. For excitation
frequencies large compared to the inverse dwell time of electrons in the dot
(i.e., GHz), we find mesoscopic fluctuations of induced current that are fully
asymmetric in the applied perpendicular magnetic field, as predicted by recent
theory. Conductance, measured simultaneously, is found to be symmetric in
field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is
always symmetric in field, suggesting its origin is mesoscopic rectification.Comment: related papers at http://marcuslab.harvard.ed
Semiclassical theory of a quantum pump
In a quantum charge pump, the periodic variation of two parameters that
affect the phase of the electronic wavefunction causes the flow of a direct
current. The operating mechanism of a quantum pump is based on quantum
interference, the phases of interfering amplitudes being modulated by the
external parameters. In a ballistic quantum dot, there is a minimum time before
which quantum interference can not occur: the Ehrenfest time. Here we calculate
the current pumped through a ballistic quantum dot when the Ehrenfest time is
comparable to the mean dwell time. Remarkably, we find that the pumped current
has a component that is not suppressed if the Ehrenfest time is much larger
than the mean dwell time.Comment: 14 pages, 8 figures. Revised version, minor change
Reformation and transformation of charity work at the beginning of the new time
This article is aimed at studying the transformation of Christian charity at the beginning of the New Time and the analysis of changes ongoing in this sphere. The authors of this research start with the analysis of the situation that had been formed in the economy, culture and activity of the Roman Catholic Church in the late Middle Ages. Such a preliminary excursion into the historical domain is not coincidental. It assists understanding the reasons for the Reformation and later events. However, “in the beginning was the Word”, therefore, the text analyzes the ideas of such founding fathers of Protestantism as Martin Luther, John Calvin, Huldrych Zwingli. The new ideology along with the sociocultural and socioeconomic factors promoted the formation of a radically different and more creative social system, also including the charity sphere that became more rational, practical and rough
Photovoltaic Current Response of Mesoscopic Conductors to Quantized Cavity Modes
We extend the analysis of the effects of electromagnetic (EM) fields on
mesoscopic conductors to include the effects of field quantization, motivated
by recent experiments on circuit QED. We show that in general there is a
photovoltaic (PV) current induced by quantized cavity modes at zero bias across
the conductor. This current depends on the average photon occupation number and
vanishes identically when it is equal to the average number of thermal
electron-hole pairs. We analyze in detail the case of a chaotic quantum dot at
temperature T_e in contact with a thermal EM field at temperature T_f,
calculating the RMS size of the PV current as a function of the temperature
difference, finding an effect ~pA.Comment: 4 pages, 2 figure
Temperature Dependence of Magnetophonon Resistance Oscillations in GaAs/AlAs Heterostructures at High Filling Factors
The temperature dependence of phonon-induced resistance oscillations has been
investigated in two-dimensional electron system with moderate mobility at large
filling factors at temperature range T = 7.4 - 25.4 K. The amplitude of
phonon-induced oscillations has been found to be governed by quantum relaxation
time which is determined by electron-electron interaction effects. This is in
agreement with results recently obtained in ultra-high mobility two-dimensional
electron system with low electron density [A. T. Hatke et al., Phys. Rev. Lett.
102, 086808 (2009)]. The shift of the main maximum of the magnetophonon
resistance oscillations to higher magnetic fields with increasing temperature
is observed.Comment: 5 pages, 4 figure
The status of world outlook and environmental competencies in aerospace engineering training: the general and special
The article is devoted to the study of the status of philosophical and environmental competences for engineering education programs in the field of space exploration. The authors prove that the specialists who will work in the space field in the XXI century face the most important problems, the solution of which is vital for humanity. It is stated that the quality of future decisions will be determined by the development of the philosophical and environmental ideas. It is demonstrated that these idea should necessarily have futurological character. It is suggested that the special courses aimed at the formation of futurological philosophical and environmental concepts can present as a possible solution to this problem (e.g. Creativity training for engineers, etc.)
- …