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E. R. Mucciolo

Publications and source records attributed to E. R. Mucciolo.

28 records · Page 2Linked to original sources
arXiv2003

Statistical fluctuations of pumping and rectification currents in quantum dots

We investigate the statistical fluctuations of currents in chaotic quantum dots induced by pumping and rectification at finite temperature and in the presence of dephasing. In open quantum dots, dc currents can be generated by the action of two equal-frequency ac gate voltages. The adiabatic regime occurs when the driving frequency is smaller than the electron inverse dwell time. Using numerical simulations complemented by semiclassical calculations, we consider both limits of small and large number of propagating channels in the leads when time-reversal symmetry is fully broken. We find that at intermediate temperature regimes, namely, $k_BT \alt Δ$, where $Δ$ is the mean single-particle level spacing, thermal smearing suppresses the current amplitude more effectively than dephasing. Motivated by recent theoretical and experimental works, we also study the statistics of rectified currents in the presence of a parallel, Zeeman splitting, magnetic field.

cond-mat.mes-hall↗
arXiv2001

Measuring the Lyapunov exponent using quantum mechanics

We study the time evolution of two wave packets prepared at the same initial state, but evolving under slightly different Hamiltonians. For chaotic systems, we determine the circumstances that lead to an exponential decay with time of the wave packet overlap function. We show that for sufficiently weak perturbations, the exponential decay follows a Fermi golden rule, while by making the difference between the two Hamiltonians larger, the characteristic exponential decay time becomes the Lyapunov exponent of the classical system. We illustrate our theoretical findings by investigating numerically the overlap decay function of a two-dimensional dynamical system.

nlin.CD↗
arXiv1999

Electron transport through a mesoscopic metal-CDW-metal junction

In this work we study the transport properties of a finite Peierls-Fröhlich dielectric with a charge density wave of the commensurate type. We show that at low temperatures this problem can be mapped onto a problem of fractional charge transport through a finite-length correlated dielectric, recently studied by Ponomarenko and Nagaosa [Phys. Rev. Lett {\bf 81}, 2304 (1998)]. The temperature dependence of conductance of the charge density wave junction is presented for a wide range of temperatures.

cond-mat.mes-hall↗
arXiv1998

Transport properties of quasiparticles with fractional exclusion statistics

We consider the ballistic transport of quasiparticles with exclusion statistics through a 1D wire within the Landauer-Buttiker approach. We demonstrate that quasiparticle transport coefficients (electrical and heat conductance, as well as thermopower) are determined by the same general formulae as for particles with normal statistics. By applying the developed formalism to the ballistic transport of fractional charge it is shown that for a wire in contact to quasiparticles reservoirs the transport coefficients depend on the fractional charge. Specific features of resonant tunneling of quasiparticles are discussed.

cond-mat↗
arXiv1997

Parametric statistics of the scattering matrix: From metallic to insulating quasi-unidimensional disordered systems

We investigate the statistical properties of the scattering matrix $S$ describing the electron transport through quasi-one dimensional disordered systems. For weak disorder (metallic regime), the energy dependence of the phase shifts of $S$ is found to yield the same universal parametric correlations as those characterizing chaotic Hamiltonian eigenvalues driven by an external parameter. This is analyzed within a Brownian-motion model for $S$, which is directly related to the distribution of the Wigner-Smith delay time matrix. For large disorder (localized regime), transport is dominated by resonant tunneling and the universal behavior disappears. A model based on a simplified description of the localized wave functions qualitatively explains our numerical results. In the insulator, the parametric correlation of the phase shift velocities follows the energy-dependent autocorrelator of the Wigner time. The Wigner time and the conductance are correlated in the metal and in the insulator.

cond-mat.mes-hall↗
arXiv1995

Sensitivity of quantum chaotic wavefunction intensities to changes in external perturbations

We examine the sensitivity of wavefunction intensities in chaotic quantum systems to small changes in an arbitrary external perturbation. A universal scaling is proposed for all three Dyson ensembles and a novel theoretical approach is used to determine exact expressions for systems which violate T-invariance. Analytical results are compared with numerical simulations of tight-binding Anderson Hamiltonians.

cond-mat↗
arXiv1994

Statistical Properties of Level Widths and Conductance Peaks in a Quantum Dot

We study the statistics of level widths of a quantum dot with extended contacts in the absence of time-reversal symmetry. The widths are determined by the amplitude of the wavefunction averaged over the contact area. The distribution function of level widths for a two-point contact is evaluated exactly. The distribution resembles closely the result obtained when the wavefunction fluctuates independently at each point, but differs from the one-point case. Analytical calculations and numerical simulations show that the distribution for many-point contacts has a power-law behavior at small level widths. The exponent is given by the number of points in the lead and diverges in the continuous limit. The distribution of level widths is used to determine the distribution of conductance peaks in the resonance regime. At intermediate temperatures, we find that the distribution tends to normal and fluctuations in the height of the peaks are suppressed as the lead size is increased.

cond-mat↗
arXiv1994

Manifestation of Quantum Chaos in Electronic Band Structures

We use semiconductors as an example to show that quantum chaos manifests itself in the energy spectrum of crystals. We analyze the {\it ab initio} band structure of silicon and the tight-binding spectrum of the alloy $Al_xGa_{1-x}As$, and show that some of their statistical properties obey the universal predictions of quantum chaos derived from the theory of random matrices. Also, the Bloch momenta are interpreted as external, tunable, parameters, acting on the reduced (unit cell) Hamiltonian, in close analogy to Aharonov-Bohm fluxes threading a torus. They are used in the investigation of the parametric autocorrelator of crystal velocities. We find that our results are in good agreement with the universal curves recently proposed by Simons and coworkers.

cond-mat↗
arXiv1993

Exact Dynamical Correlations of the 1/r^2 Model

We present exact results for the dynamical structure function, i.e.~the density-density correlations for the 1/r^2 system of interacting particles at three special values of the coupling constant. The results are interpreted in terms of exact excitations of the model which are available from Bethe's Ansatz, thereby throwing light on the quasi-particle content of the elementary excitations. We also obtain the first moment of the discrete version of the model, which provides a non-trivial check on its structure function. We show that the property of spectrum saturation is a common feature of both versions.

cond-mat↗