212 research outputs found
Weak measurement of cotunneling time
Quantum mechanics allows the existence of "virtual states" that have no
classical analogue. Such virtual states defy direct observation through strong
measurement, which would destroy the volatile virtual state. Here we show how a
virtual state of an interacting many-body system can be detected employing a
weak measurement protocol with postselection. We employ this protocol for the
measurement of the time it takes an electron to tunnel through a virtual state
of a quantum dot (cotunneling). Contrary to classical intuition, this
cotunneling time is independent of the strength of the dot-lead coupling and
may deviate from that predicted by time-energy uncertainty relation. Our
approach, amenable to experimental verification, may elucidate an important
facet of quantum mechanics which hitherto was not accessible by direct
measurements.Comment: 13 pages, 5 figures, 1 tabl
Coherence and Partial Coherence in Interacting Electron Systems
We study coherence of electron transport through interacting quantum dots and
discuss the relation of the coherent part to the flux-sensitive conductance for
three different types of Aharonov-Bohm interferometers. Contributions to
transport in first and second order in the intrinsic line width of the dot
levels are addressed in detail. We predict an asymmetry of the interference
signal around resonance peaks as a consequence of incoherence associated with
spin-flip processes. Furthermore, we show by strict calculation that
first-order contributions can be partially or even fully coherent. This
contrasts with the sequential-tunneling picture which describes first-order
transport as a sequence of incoherent tunneling processes
The Effect of Interaction on Shot Noise in The Quantum Limit
We employ a non-linear sigma model defined on a Keldysh contour to study the
current and the current noise in a diffusive micro-bridge in the presence of
electron-electron interactions. Out of equilibrium the fluctuation-dissipation
theorem (FDT) does not apply, hence these two quantities are not simply
interrelated. For a two-dimensional electron gas (2DEG) we obtain logarithmic
singularities in the low frequency limit. PACS Nos. 71.10.Ay, 71.23.An,
73.50.TdComment: Submitted to the proceedings of 36 Renconters de Moriond "Electronic
correlations: from meso- to nano-physics". One figure adde
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