S. Oberholzer

1/3-shot-noise suppression in diffusive nanowires

We report low-temperature shot-noise measurements of short diffusive Au wires attached to electron reservoirs of varying sizes. The measured noise suppression factor compared to the classical noise value

Molecular States in Carbon Nanotube Double Quantum Dots

2e|I|

Giant fluctuations and gate control of the g-factor in InAs nanowire quantum dots

strongly depends on the electric heat conductance of the reservoirs. For small reservoirs injection of hot electrons increases the measured noise, and hence the suppression factor. The universal

Crossover between classical and quantum shot noise in chaotic cavities.

1/3

Shot Noise by Quantum Scattering in Chaotic Cavities

suppression factor can only asymptotically be reached for macroscopically large and thick electron reservoirs. A heating model based on the Wiedemann-Franz law is used to explain this effect.

The Hanbury Brown and Twiss experiment with fermions

We report electrical transport measurements through a semiconducting single-walled carbon nanotube with three additional top gates. At low temperatures the system acts as a double quantum dot with large interdot tunnel coupling allowing for the observation of tunnel-coupled molecular states extending over the whole double-dot system. We precisely extract the tunnel coupling and identify the molecular states by the sequential-tunneling line shape of the resonances in differential conductance.

Finite-bias visibility dependence in an electronic Mach-Zehnder interferometer

We study the g-factor of discrete electron states in InAs nanowire based quantum dots. The g values are determined from the magnetic field splitting of the zero bias anomaly due to the spin 1/2 Kondo effect. Unlike to previous studies based on 2DEG quantum dots, the g-factors of neighboring electron states show a surprisingly large fluctuation: g can scatter between 2 and 18. Furthermore electric gate tunability of the g-factor is demonstrated.

Scaling of 1/f noise in tunable break-junctions

The discreteness of charge in units of e led Schottky in 1918 to predict that the electrical current in a vacuum tube fluctuates even if all spurious noise sources are eliminated carefully. This phenomenon is now widely known as shot noise. In recent years, shot noise in mesoscopic conductors, where charge motion is quantum-coherent over distances comparable to the system size, has been studied extensively. In those experiments, charge does not propagate as an isolated entity through free space, as for vacuum tubes, but is part of a degenerate and quantum-coherent Fermi sea of charges. It has been predicted that shot noise in mesoscopic conductors can disappear altogether when the system is tuned to a regime where electron motion becomes classically chaotic. Here we experimentally verify this prediction by using chaotic cavities where the time that electrons dwell inside can be tuned. Shot noise is present for large dwell times, where the electron motion through the cavity is ‘smeared’ by quantum scattering, and it disappears for short dwell times, when the motion becomes classically deterministic.

Shot-noise and conductance measurements of transparent superconductor/two-dimensional electron gas junctions

We have experimentally studied shot noise of chaotic cavities defined by two quantum point contacts in series. The cavity noise is determined as (1/4)2e/I/ in agreement with theory and can be well distinguished from other contributions to noise generated at the contacts. Subsequently, we have found that cavity noise decreases if one of the contacts is further opened and reaches nearly zero for a highly asymmetric cavity. Heating inside the cavity due to electron-electron interaction can slightly enhance the noise of large cavities and is also discussed quantitatively.

Shot noise of series quantum point contacts intercalating chaotic cavities

Abstract We realized an equivalent Hanbury Brown and Twiss experiment for a beam of electrons in a two-dimensional electron gas in the quantum Hall regime. A metallic split gate serves as a tunable beam splitter which is used to partition the incident beam into transmitted and reflected partial beams. The current fluctuations in the reflected and transmitted beam are fully anticorrelated demonstrating that fermions tend to exclude each other (anti-bunching). If the occupation probability of the incident beam is lowered by an additional gate, the anticorrelation is reduced and disappears in the classical limit of a highly diluted beam.