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Maura Sassetti

Publications and source records attributed to Maura Sassetti.

88 records · Page 5Linked to original sources
arXiv2007

Sub-Poissonian phononic population in a nanoelectromechanical system

Population of a phononic mode coupled to a single-electron transistor in the sequential tunneling regime is discussed for the experimentally realistic case of intermediate electron-phonon coupling. Features like a sub-Poissonian bosonic distribution are found in regimes where electron transport drives the oscillator strongly out of equilibrium with only few phonon states selectively populated. The electron Fano factor is compared to fluctuations in the phonon distribution, showing that all possible combinations of sub- and super-Poissonian character can be realized.

cond-mat.mes-hall↗
arXiv2007

Environmental noise reduction for holonomic quantum gates

We study the performance of holonomic quantum gates, driven by lasers, under the effect of a dissipative environment modeled as a thermal bath of oscillators. We show how to enhance the performance of the gates by suitable choice of the loop in the manifold of the controllable parameters of the laser. For a simplified, albeit realistic model, we find the surprising result that for a long time evolution the performance of the gate (properly estimated in terms of average fidelity) increases. On the basis of this result, we compare holonomic gates with the so-called stimulated Raman adiabatic passage (STIRAP) gates.

quant-ph↗
arXiv2007

Transport of fractional Hall quasiparticles through an antidot

Current statistics of an antidot in the fractional quantum Hall regime is studied for Laughlin's series. The chiral Luttinger liquid picture of edge states with a renormalized interaction exponent $g$ is adopted. Several peculiar features are found in the sequential tunneling regime. On one side, current displays negative differential conductance and double-peak structures when $g<1$. On the other side, universal sub-poissonian transport regimes are identified through an analysis of higher current moments. A comparison between Fano factor and skewness is proposed in order to clearly distinguish the charge of the carriers, regardless of possible non-universal interaction renormalizations. Super-poissonian statistics is obtained in the shot limit for $g<1$, and plasmonic effects due to the finite-size antidot are tracked.

cond-mat.mes-hall↗
arXiv2006

Fidelity optimization for holonomic quantum gates in dissipative environments

We analyze the performance of holonomic quantum gates in semi-conductor quantum dots, driven by ultrafast lasers, under the effect of a dissipative environment. In agreement with the standard practice, the environment is modeled as a thermal bath of oscillators linearly coupled with the excitonic states of the quantum dot. Standard techniques of quantum dissipation make the problem amenable to a numerical treatment and allow to determine the fidelity (the common gate-performance estimator), as a function of all the relevant physical parameters. As a consequence of our analysis, we show that, by varying in a suitable way the controllable parameters, the disturbance of the environment can be (approximately) suppressed, and the performance of the gate optimized--provided that the thermal bath is purely superhomic. We conclude by showing that such an optimization it is impossible for ohmic environments.

quant-ph↗
arXiv2006

Electron conductivity and second generation Composite Fermions

The relation between the conductivity tensors of Composite Fermions and electrons is extended to second generation Composite Fermions. It is shown that it crucially depends on the coupling matrix for the Chern-Simons gauge field. The results are applied to a model of interacting Composite Fermions that can explain both the anomalous plateaus in spin polarization and the corresponding maxima in the resistivity observed in recent transport experiments.

cond-mat.mes-hall↗
arXiv2003

On ground states of interacting Composite Fermions with spin at half filling

The effects of interactions in a 2D electron system in a strong magnetic field of two degenerate Landau levels with opposite spins and at filling factors 1/2 are studied. Using the Chern-Simons gauge transformation, the system is mapped to Composite Fermions. The fluctuations of the gauge field induce an effective interaction between the Composite Fermions which can be attractive in both the particle-particle and in the particle-hole channel. As a consequence, a spin-singlet (s-wave) ground state of Composite Fermions can exist with a finite pair-breaking energy gap for particle-particle or particle-hole pairs. The competition between these two possible ground states is discussed. For long-range Coulomb interaction the particle-particle state is favored if the interaction strength is small. With increasing interaction strength there is a crossover towards the particle-hole state. If the interaction is short range, only the particle-particle state is possible.

cond-mat.mes-hall↗
arXiv2001

Control of spin in quantum dots with non-Fermi liquid correlations

Spin effects in the transport properties of a quantum dot with spin-charge separation are investigated. It is found that the non-linear transport spectra are dominated by spin dynamics. Strong spin polarization effects are observed in a magnetic field. They can be controlled by varying gate and bias voltages. Complete polarization is stable against interactions. When polarization is not complete, it is power-law enhanced by non-Fermi liquid effects.

cond-mat.str-el↗
arXiv1999

Anomalous Tien-Gordon scaling in a 1d tunnel junction

We investigate the nonlinear ac transport through a quantum wire with an impurity in the presence of finite range electron-electron interactions. We discuss the influence of the spatial shape of the ac electric field onto transport properties of the system and find that the scaling behavior of the occupation probability of the sidebands depends on the range of the voltage drop.

cond-mat.mes-hall↗
arXiv1999

Local fields in nonlinear quantum transport

We investigate the dynamical interplay between currents and electromagnetic fields in frequency-dependent transport through a single-channel quantum wire with an impurity potential in the presence of electron-electron interactions. We introduce and discuss a formalism which allows a self-consistent treatment of currents and electromagnetic fields.

cond-mat.mes-hall↗
arXiv1999

Frequency scaling of photo-induced tunneling

The DC current-voltage characteristics, induced by a driving electric field with frequency Omega, of a one dimensional electron channel with a tunnel barrier is calculated. Electron-electron interaction of finite-range is taken into account. For intermediate interaction strengths, the non-linear differential conductance shows cusp-like minima at bias voltages integer multiples of hbar Omega / e that are a consequence of the finite non-zero range of the interaction but are independent of the shape of the driving electric field. However, the frequency-scaling of the photo-induced current shows a cross-over between Omega^{-1} and Omega^{-2}, and depends on the spatial shape of the driving field and the range of the interaction.

cond-mat.mes-hall↗
arXiv1998

Resonant Raman scattering by collective modes of the one-dimensional electron gas

We show that the low-energy peak in the polarized resonant Raman spectra of quantum wires, which is commonly associated with ``single particle excitations'', can be interpreted as signature of intra-band collective spin excitations. A broad maximum in the resonant depolarized spectra is predicted to exist above the frequency of the spin density excitation, due to simultaneous but independent propagation of spin- and charge-density modes.

cond-mat.str-el↗
arXiv1997

AC-conductance of a quantum wire with electron-electron interaction

The complex ac-response of a quasi-one dimensional electron system in the one-band approximation with an interaction potential of finite range is investigated. It is shown that linear response is exact for this model. The influence of the screening of the electric field is discussed. The complex absorptive conductance is analyzed in terms of resistive, capacitive and inductive behaviors.

cond-mat.mes-hall↗
arXiv1997

Tunneling between two Luttinger liquids with long range interaction

The non linear charge transfer through a tunnel junction between two Luttinger systems is studied for repulsive, finite range interaction between electrons on the same, V_{11}, and on different,V_{12}, sides of the junction. Features of the Coulomb blockade effect are observed if V_{12}=0. We predict a novel interaction induced enhancement of the current if V_{12}>0. When V_{12}=V_{11}, the current is suppressed at small bias, but the ``charging energy'', obtained from the asymptotic behavior at high bias voltage, vanishes.

cond-mat.mes-hall↗
arXiv1997

Coulomb blockade at a tunnel junction between two quantum wires with long-range interaction

The non-linear current-voltage characteristic of a tunnel junction between two Luttinger systems is calculated for an interaction with finite range. Coulomb blockade features are found. The dissipative resistance, the capacitance and the external impedance, which were introduced ad hoc in earlier theories, are obtained in terms of the electron-electron interaction. The frequency dependence of the impedance is given by the excitation spectrum of the electrons.

cond-mat.mes-hall↗
arXiv1995

Low-temperature nonequilibrium transport in a Luttinger liquid

The temperature-dependent nonlinear conductance for transport of a Luttinger liquid through a barrier is calculated in the nonperturbative regime for $g=1/2-ε$, where $g$ is the dimensionless interaction constant. To describe the low-energy behavior, we perform a leading-log summation of all diagrams contributing to the conductance which is valid for $|ε| << 1$. With increasing external voltage, the asymptotic low-temperature behavior displays a turnover from the $T^{2/g-2}$ to a universal $T^2$ law.

cond-mat↗