5,468 research outputs found
Shot-noise in transport and beam experiments
Consider two Fermi gases with the same {\it average} currents: a transport
gas, as in solid-state experiments where the chemical potentials of terminal 1
is and of terminal 2 and 3 is , and a beam, i.e., electrons
entering only from terminal 1 having energies between and . By
expressing the current noise as a sum over single-particle transitions we show
that the temporal current fluctuations are very different: The beam is noisier
due to allowed single-particle transitions into empty states below .
Surprisingly, the correlations between terminals 2 and 3 are the same.Comment: 4 pages, 2 figure
Pairing and persistent currents - the role of the far levels
We calculate the orbital magnetic response to Aharonov Bohm flux of
disordered metallic rings with attractive pairing interaction. We consider the
reduced BCS model, and obtain the result as an expansion of its exact solution
to first order in the interaction. We emphasize the connection between the
large magnetic response and the finite occupation of high energy levels in the
many-body ground state of the ring.Comment: 10 pages, contribution to MS+S200
Quantized adiabatic quantum pumping due to interference
Recent theoretical calculations, demonstrating that quantized charge transfer
due to adiabatically modulated potentials in mesoscopic devices can result
purely from the interference of the electron wave functions (without invoking
electron-electron interactions) are reviewed: (1) A new formula is derived for
the pumped charge Q (per period); It reproduces the Brouwer formula without a
bias, and also yields the effect of the modulating potential on the Landauer
formula in the presence of a bias. (2) For a turnstile geometry, with
time-dependent gate voltages V_L(t) and V_R(t), the magnitude and sign of Q are
determined by the relative position and orientation of the closed contour
traversed by the system in the {V_L-V_R} plane, relative to the transmission
resonances in that plane. Integer values of Q (in units of e) are achieved when
a transmission peak falls inside the contour, and are given by the winding
number of the contour. (3) When the modulating potential is due to surface
acoustic waves, Q exhibits a staircase structure, with integer values,
reminiscent of experimental observations.Comment: Invited talk, Localization, Tokyo, August 200
Transmission of two interacting electrons
The transmission of two electrons through a region where they interact is
found to be enhanced by a renormalization of the repulsive interaction. For a
specific example of the single-particle Hamiltonian, which includes a strongly
attractive potential, the renormalized interaction becomes attractive, and the
transmission has a pronounced maximum as function of the depth of the
single-electron attractive potential. The results apply directly to a simple
model of scattering of two interacting electrons by a quantum dot.Comment: 12 pages, 2 figure
- …