Single-Electron Effects in a Coupled Dot-Ring System

Aharonov-Bohm oscillations are studied in the magnetoconductance of a micron-sized open quantum ring coupled capacitively to a Coulomb-blockaded quantum dot. As the plunger gate of the dot is modulated and tuned through a conductance resonance, the amplitude of the Aharonov-Bohm oscillations in the transconductance of the ring displays a minimum. We demonstrate that the effect is due to a single-electron screening effect, rather than to dephasing. Aharonov-Bohm oscillations in a quantum ring can thus be used for the detection of single charges.Comment: 5 pages, 3 figure

Low-Frequency Noise Phenomena in Switched MOSFETs

In small-area MOSFETs widely used in analog and RF circuit design, low-frequency (LF) noise behavior is increasingly dominated by single-electron effects. In this paper, the authors review the limitations of current compact noise models which do not model such single-electron effects. The authors present measurement results that illustrate typical LF noise behavior in small-area MOSFETs, and a model based on Shockley-Read-Hall statistics to explain the behavior. Finally, the authors treat practical examples that illustrate the relevance of these effects to analog circuit design. To the analog circuit designer, awareness of these single-electron noise phenomena is crucial if optimal circuits are to be designed, especially since the effects can aid in low-noise circuit design if used properly, while they may be detrimental to performance if inadvertently applie

Transport Properties of Carbon Nanotube C60_{60} Peapods

We measure the conductance of carbon nanotube peapods from room temperature down to 250mK. Our devices show both metallic and semiconducting behavior at room temperature. At the lowest temperatures, we observe single electron effects. Our results suggest that the encapsulated C$_{60}$ molecules do not introduce substantial backscattering for electrons near the Fermi level. This is remarkable given that previous tunneling spectroscopy measurements show that encapsulated C$_{60}$ strongly modifies the electronic structure of a nanotube away from the Fermi level.Comment: 9 pages, 4 figures. This is one of two manuscripts replacing the one orginally submitted as arXiv:cond-mat/0606258. The other one is arXiv:0704.3641 [cond-mat

Single-electron transistor made of multiwalled carbon nanotube using scanning probe manipulation

We positioned semiconducting multiwalled carbon nanotube, using an atomic force microscope, between two gold electrodes at SiO2 surface. Transport measurements exhibit single-electron effects with a charging energy of 24 K. Using the Coulomb staircase model, the capacitances and resistances between the tube and the electrodes can be characterized in detail.Peer reviewe

Quantum Phase Transitions and Vortex Dynamics in Superconducting Networks

Josephson junction arrays are ideal model systems where a variety of phenomena, phase transitions, frustration effects, vortex dynamics, chaos, to mention a few of them, can be studied in a controlled way. In this review we focus on the quantum dynamical properties of low capacitance Josephson junction arrays. The two characteristic energy scales in these systems are the Josephson energy, associated to the tunneling of Cooper pairs between neighboring islands, and the charging energy, which is the energy cost to add an extra electron charge to a neutral island. The phenomena described in this review stem from the competition between single electron effects with the Josephson effect. One example is the (quantum) Superconductor-Insulator phase transition which occurs by varying the ratio between the coupling constants and/or by means of external magnetic/electric fields. We will describe how the phase diagram depends on the various control paramters and the transport properties close to the quantum critical point. The relevant topological excitations on the superconducting side of the phase diagram are vortices. In low capacitance junction arrays vortices behave as massive underdamped particles that can exhibit quantum behaviour. We will report on the various experiments and theoretical treatments on quantum vortex dynamics.Comment: To be published in Physics Reports. Better quality figures can be obtained upon reques