Markus Buttiker

Shot Noise in Mesoscopic Conductors

Abstract Theoretical and experimental work concerned with dynamic fluctuations has developed into a very active and fascinating subfield of mesoscopic physics. We present a review of this development focusing on shot noise in small electric conductors. Shot noise is a consequence of the quantization of charge. It can be used to obtain information on a system which is not available through conductance measurements. In particular, shot noise experiments can determine the charge and statistics of the quasiparticles relevant for transport, and reveal information on the potential profile and internal energy scales of mesoscopic systems. Shot noise is generally more sensitive to the effects of electron–electron interactions than the average conductance. We present a discussion based on the conceptually transparent scattering approach and on the classical Langevin and Boltzmann–Langevin methods; in addition a discussion of results which cannot be obtained by these methods is provided. We conclude the review by pointing out a number of unsolved problems and an outlook on the likely future development of the field.

Josephson behavior in small normal one-dimensional rings

Abstract Small and strictly one-dimensional rings of normal metal, driven by an external magnetic flux, act like superconducting rings with a Josephson junction, except that 2e is replaced by e.

Capacitance, admittance, and rectification properties of small conductors

We formulate microscopic expressions for capacitances, admittances and the rectification properties for small phase-coherent samples consisting of a number of metallic layers separated by insulators. The electric potential in such a structure is discussed with the help of characteristic functions which determine the variation of the microscopic potential inside the sample in response to an increase of the electro-chemical potential at a contact. An electrochemical capacitance matrix is derived which allows for field penetration into the conductor. We discuss the admittance matrix for conductors with nearby capacitors (gates) and analyse its magnetic field symmetry. We use the characteristic potentials to discuss the rectification properties of a conduction channel in the presence of nearby capacitors.

Attosecond ionization and tunneling delay time measurements in helium.

It is well established that electrons can escape from atoms through tunneling under the influence of strong laser fields, but the timing of the process has been controversial and far too rapid to probe in detail. We used attosecond angular streaking to place an upper limit of 34 attoseconds and an intensity-averaged upper limit of 12 attoseconds on the tunneling delay time in strong field ionization of a helium atom. The ionization field derives from 5.5-femtosecond-long near-infrared laser pulses with peak intensities ranging from 2.3 × 1014 to 3.5 × 1014 watts per square centimeter (corresponding to a Keldysh parameter variation from 1.45 to 1.17, associated with the onset of efficient tunneling). The technique relies on establishing an absolute reference point in the laboratory frame by elliptical polarization of the laser pulse, from which field-induced momentum shifts of the emergent electron can be assigned to a temporal delay on the basis of the known oscillation of the field vector.

Floquet scattering theory of quantum pumps

We develop the Floquet scattering theory for quantum-mechanical pumping in mesoscopic conductors. The nonequilibrium distribution function, the dc charge, and heat currents are investigated at arbitrary pumping amplitude and frequency. For mesoscopic samples with a discrete spectrum we predict a sign reversal of the pumped current when the pump frequency is equal to the level spacing in the sample. This effect allows us to measure the phase of the transmission coefficient through the mesoscopic sample. We discuss the necessary symmetry conditions (both spatial and temporal) for pumping.

Dissipation and noise in adiabatic quantum pumps

We investigate the distribution function, the heat flow, and the noise properties of an adiabatic quantum pump for an arbitrary relation of pump frequency

Optimal energy quanta to current conversion

\ensuremath{\omega}

Scattering Theory of Photon-Assisted Electron Transport

and temperature. To achieve this we start with the scattering matrix approach for ac transport. This approach leads to expressions for the quantities of interest in terms of the sidebands of particles exiting the pump. The sidebands correspond to particles which have gained or lost a modulation quantum

Friedel phases and phases of transmission amplitudes in quantum scattering systems

\ensuremath{\Elzxh}\ensuremath{\omega}.

Aharonov-Bohm oscillations in a mesoscopic ring with a quantum dot.

We find that our results for the pump current, the heat flow, and the noise can all be expressed in terms of a parametric emissivity matrix. In particular we find that the current cross correlations of a multiterminal pump are directly related to a nondiagonal element of the parametric emissivity matrix. The approach allows a description of the quantum statistical correlation properties (noise) of an adiabatic quantum pump.