Tunable Fermi-Edge Resonance in an Open Quantum Dot

Resonant tunneling in an open mesoscopic quantum dot is proposed as a vehicle to realize a tunable Fermi-edge resonance with variable coupling strength. We solve the x-ray edge problem for a generic nonseparable scatterer and apply it to describe tunneling in a quantum dot. The tunneling current power law exponent is linked to the S-matrix of the dot. The control of scattering by varying the dot shape and coupling to the leads allows to explore a wide range of exponents. Transport properties, such as weak localization, mesoscopic conductance fluctuations, and sensitivity to Wigner-Dyson ensemble type, have their replicas in the Fermi-edge singularity.Comment: 4 pages, 3 figure

Allowed charge transfers between coherent conductors driven by a time-dependent scatterer

We derive constraints on the statistics of the charge transfer between two conductors in the model of arbitrary time-dependent instant scattering of non-interacting fermions at zero temperature. The constraints are formulated in terms of analytic properties of the generating function: its zeroes must lie on the negative real axis. This result generalizes existing studies for scattering by a time-independent scatterer under time-dependent bias voltage.Comment: 5 pages, no figures, corrected misprints and minor changes in version

Full Current Statistics of Incoherent "Cold Electrons"

We evaluate the full current statistics (FCS) in the low dimensional (1D and 2D) diffusive conductors in the incoherent regime, $eV\gg E_{\rm Th}=D/L^2$, $E_{\rm Th}$ being the Thouless energy. It is shown that Coulomb interaction substantially enhances the probability of big current fluctuations for short conductors with $E_{\rm Th}\gg1/\tau_E$, $\tau_E$ being the energy relaxation time, leading to the exponential tails in the current distribution. The current fluctuations are most strong for low temperatures, provided $E_{\rm Th}\sim [(eV)^2/D\nu_1^2\bigr]^{1/3}$ for 1D and $E_{\rm Th}\sim (eV/g)\ln g$ for 2D, where $g$ is a dimensionless conductance and $\nu_1$ is a 1D density of states. The FCS in the "hot electron" regime is also discussed.Comment: 4 pages, 1 table, 2 figure

Factorization of quantum charge transport for non-interacting fermions

We show that the statistics of the charge transfer of non-interacting fermions through a two-lead contact is generalized binomial, at any temperature and for any form of the scattering matrix: an arbitrary charge-transfer process can be decomposed into independent single-particle events. This result generalizes previous studies of adiabatic pumping at zero temperature and of transport induced by bias voltage.Comment: 13 pages, 3 figures, typos corrected, references adde

Peierls-type Instability and Tunable Band Gap in Functionalized Graphene

Functionalizing graphene was recently shown to have a dramatic effect on the electronic properties of this material. Here we investigate spatial ordering of adatoms driven by the RKKY-type interactions. In the ordered state, which arises via a Peierls-instability-type mechanism, the adatoms reside mainly on one of the two graphene sublattices. Bragg scattering of electron waves induced by sublattice symmetry breaking results in a band gap opening, whereby Dirac fermions acquire a finite mass. The band gap is found to be immune to the adatoms' positional disorder, with only an exponentially small number of localized states residing in the gap. The gapped state is stabilized in a wide range of electron doping. Our findings show that controlled adsorption of adatoms or molecules provides a route to engineering a tunable band gap in graphene.Comment: 6 pgs, 3 fg