Universal self-assembly of one-component three-dimensional dodecagonal quasicrystals

Using molecular dynamics simulations, we study computational self-assembly of one-component three-dimensional dodecagonal (12-fold) quasicrystals in systems with two-length-scale potentials. Existing criteria for three-dimensional quasicrystal formation are quite complicated and rather inconvenient for particle simulations. So to localize numerically the quasicrystal phase, one should usually simulate over a wide range of system parameters. We show how to universally localize the parameters values at which dodecagonal quasicrystal order may appear for a given particle system. For that purpose, we use a criterion recently proposed for predicting decagonal quasicrystal formation in one-component two-length-scale systems. The criterion is based on two dimensionless effective parameters describing the fluid structure which are extracted from radial distribution function. The proposed method allows reducing the time spent for searching the parameters favoring certain solid structure for a given system. We show that the method works well for dodecagonal quasicrystals; this results is verified on four systems with different potentials: Dzugutov potential, oscillating potential which mimics metal interactions, repulsive shoulder potential describing effective interaction for core/shell model of colloids and embedded-atom model potential for aluminum. Our results suggest that mechanism of dodecagonal quasicrystal formation is universal for both metallic and soft-matter systems and it is based on competition between interparticle scales.Comment: 8 pages, 6 figure

Single Flux Transistor: the controllable interplay of Coherent Quantum Phase Slip and Flux quantization

The Single Cooper Pair Josephson Transistor is a device that exhibits at the same time charge quantization and phase coherence. Coherent quantum phase slip phenomenon is "dual" the Josephson phase coherence while the charge quantization is dual to the flux quantization. We present the experimental demonstration and the theoretical description of a new superconducting device - Single Flux Transistor, which is dual to the Single Cooper Pair Transistor. Our transport measurements show the periodic modulation of the critical voltage by the external magnetic field. The obtained current-voltage characteristics show the hysteretic behavior, which we attribute to the intrinsic self-heating of charge carriers.Comment: 5 pages, 4 figure

Noise correlations, entanglement, and Bell inequalities

The aim of this chapter is to describe two situations where positive noise correlations can be directly monitored using a transport experiment, either with a superconductor or with a correlated electron system. To be more precise, the present text reflects the presentations made by the three authors during the Delft NATO workshop. Bell inequalities and quantum mechanical non-locality with electrons injected from a superconductor will be addressed first. Next, noise correlations will be computed in a carbon nanotube where electrons are injected in the bulk from a STM tip. The first topic is the result of an ongoing collaboration with G. Lesovik and G. Blatter over the years. The unifying theme is that in both branched quantum circuits, entanglement is explicit and can be illustrated via noise correlations. Entanglement can be achieved either for pairs of electrons in the case of superconductor sources connected to Fermi liquid leads, or alternatively for pairs of quasiparticle excitations of the correlated electron fluid.Comment: 24 pages, 7 figures, Proceedings of the NATO ARW workshop on Quantum Noise, Y. Nazarov and Y. Blanter editors (Kluwer 2002

Charge transport through a SET with a mechanically oscillating island

We consider a single-electron transistor (SET) whose central island is a nanomechanical oscillator. The gate capacitance of the SET depends on the mechanical displacement, thus, the vibrations of the island vibrations may strongly influence the current-voltage characteristics, current noise, and higher cumulants of the current. Harmonic oscillations of the island and oscillations with random amplitude (e.g., due to the thermal activation) change the transport characteristics in a different way. The noise spectrum has a peak at the frequency of the island oscillations; when the island oscillates harmonically, the peak reduces to a $\delta$-peak. We show that knowledge of the SET transport properties helps to determine in what way the island oscillates, to estimate the amplitude, and the frequency of the oscillations