1,609 research outputs found

### Hidden quantum pump effects in quantum coherent rings

Time periodic perturbations of an electron system on a ring are examined. For
small frequencies periodic small amplitude perturbations give rise to side band
currents which in leading order are inversely proportional to the frequency.
These side band currents compensate the current of the central band such that
to leading order no net pumped current is generated. In the non-adiabatic
limit, larger pump frequencies can lead to resonant excitations: as a
consequence a net pumped current arises. We illustrate our results for a one
channel ring with a quantum dot whose barriers are modulated parametrically.Comment: 8 pages, 5 figure

### Quantum pumping: Coherent Rings versus Open Conductors

We examine adiabatic quantum pumping generated by an oscillating scatterer
embedded in a one-dimensional ballistic ring and compare it with pumping caused
by the same scatterer connected to external reservoirs. The pumped current for
an open conductor, paradoxically, is non-zero even in the limit of vanishing
transmission. In contrast, for the ring geometry the pumped current vanishes in
the limit of vanishing transmission. We explain this paradoxical result and
demonstrate that the physics underlying adiabatic pumping is the same in open
and in closed systems.Comment: 4 pages, 2 figure

### Quantized dynamics of a coherent capacitor

A quantum coherent capacitor subject to large amplitude pulse cycles can be
made to emit or reabsorb an electron in each half cycle. Quantized currents
with pulse cycles in the GHz range have been demonstrated experimentally. We
develop a non-linear dynamical scattering theory for arbitrary pulses to
describe the properties of this very fast single electron source. Using our
theory we analyze the accuracy of the current quantization and investigate the
noise of such a source. Our results are important for future scientific and
possible metrological applications of this source.Comment: 4 pages, 2 figure

### Shot noise of a mesoscopic two-particle collider

We investigate the shot noise generated by particle emission from a
mesoscopic capacitor into an edge state reflected and transmitted at a quantum
point contact (QPC). For a capacitor subject to a periodic voltage the
resulting shot noise is proportional to the number of particles (both electrons
and holes) emitted during a period. It is proportional to the product of
transmission and reflection probability of the QPC independent of the applied
voltage but proportional to the driving frequency. If two driven capacitors are
coupled to a QPC at different sides then the resulting shot noise is maximally
the sum of noises produced by each of the capacitors. However the noise is
suppressed depending on the coincidence of the emission of two particles of the
same kind.Comment: 4 pages, 2 figure

### Quantum heat fluctuations of single particle sources

Optimal single electron sources emit regular streams of particles, displaying
no low frequency charge current noise. Due to the wavepacket nature of the
emitted particles, the energy is however fluctuating, giving rise to heat
current noise. We investigate theoretically this quantum source of heat noise
for an emitter coupled to an electronic probe in the hot-electron regime. The
distribution of temperature and potential fluctuations induced in the probe is
shown to provide direct information on the single particle wavefunction
properties and display strong non-classical features.Comment: 5 pages, 2 figure

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