5,069 research outputs found
Dephasing in a quantum dot coupled to a quantum point contact
We investigate a dephasing mechanism in a quantum dot capacitively coupled to
a quantum point contact. We use a model which was proposed to explain the 0.7
structure in point contacts, based on the presence of a quasi-bound state in a
point contact. The dephasing rate is examined in terms of charge fluctuations
of electrons in the bound state. We address a recent experiment by
Avinun-Kalish {\it et al.} [Phys. Rev. Lett. {\bf 92}, 156801 (2004)], where a
double peak structure appears in the suppressed conductance through the quantum
dot. We show that the two conducting channels induced by the bound state are
responsible for the peak structure.Comment: 4 pages, 2 figure
Sudden Suppression of Electron-Transmission Peaks in Finite-Biased Nanowires
Negative differential conductance (NDC) is expected to be an essential
property to realize fast switching in future electronic devices. We here
present a thorough analysis on electron transportability of a simple
atomic-scale model consisting of square prisms, and clarify the detailed
mechanism of the occurrence of NDC phenomenon in terms of the changes of local
density of states upon applying bias voltages to the electrodes. Boosting up
bias voltages, we observe sudden suppression of transmission peaks which
results in NDC behavior in the current-voltage characteristic. This suppression
is explained by the fact that when the bias voltage exceeds a certain
threshold, the conduction channels contributing to the current flow are
suddenly closed up to deny the electron transportation.Comment: 12 text pages, 6 figure
Suppression of Shot Noise in Quantum Point Contacts in the "0.7" Regime
Experimental investigations of current shot noise in quantum point contacts
show a reduction of the noise near the 0.7 anomaly. It is demonstrated that
such a reduction naturally arises in a model proposed recently to explain the
characteristics of the 0.7 anomaly in quantum point contacts in terms of a
quasi-bound state, due to the emergence of two conducting channels. We
calculate the shot noise as a function of temperature, applied voltage and
magnetic field, and demonstrate an excellent agreement with experiments. It is
predicted that with decreasing temperature, voltage and magnetic field, the dip
in the shot noise is suppressed due to the Kondo effect.Comment: 4 pages, 1 figur
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