Ultrasmall silicon quantum dots

We report the realization of extremely small single quantum dots in p-type silicon nanowires, defined by Schottky tunnel barriers with Ni and NiSi contacts. Despite their ultrasmall size the NiSi–Si–NiSi nanowire quantum dots readily allow spectroscopy of at least ten consecutive holes, and additionally they display a pronounced excited-state...

Spin droplets in confined quantum Hall systems

Two-dimensional semiconductor quantum dots are studied in the filling-factor range 2<v<3. We find both theoretical and experimental evidence of a collective many-body phenomenon, where a fraction of the trapped electrons form an incompressible spin droplet on the highest occupied Landau level. The phenomenon occurs only when the number of...

Real-time detection of single-electron tunneling using a quantum point contact

We observe individual tunnel events of a single electron between a quantum dot and a reservoir, using a nearby quantum point contact (QPC) as a charge meter. The QPC is capacitively coupled to the dot, and the QPC conductance changes by about 1% if the number of electrons on the dot changes by one. The QPC is voltage biased and the current is...

Engineering the quantum point contact response to single-electron charging in a few-electron quantum-dot circuit

We show that the design of a quantum point contact adjacent to a quantum dot can be optimized to produce maximum sensitivity to single-electron charging in the quantum dot. Our analysis is based on the self-consistent solution of coupled three-dimensional Kohn-Sham and Poisson equations for the quantum circuit. We predict a detection sensitivity...

Spontaneous resistance switching and low-frequency noise in quantum point contacts