Quantum phase transition and Coulomb blockade effect in triangular quantum dots with interdot capacitive and tunnel couplings

The quantum phase transition and the electronic transport in a triangular quantum dot system are investigated using the numerical renormalization group method.We concentrate on the interplay between the interdot capacitive coupling V and the interdot tunnel coupling t.For small t,three dots form a local spin doublet.As t increases,due to the competition between V and t,there exist two first-order transitions with phase sequence spin-doublet-magnetic frustration phase-orbital spin singlet.When t is absent,the evolutions of the total charge on the dots and the linear conductance are of the typical Coulomb-blockade features with increasing gate voltage.While for sufficient t,the antiferromagnetic spin correlation between dots is enhanced,and the conductance is strongly suppressed for the bonding state is almost doubly occupied.

Preparation of size controllable copper nanocrystals for nonvolatile memory applications

A method of fabricating Cu nanocrystals embedded in SiO2 dielectric film for nonvolatile memory applications by magnetron sputtering is introduced in this paper. The average size and distribution density of Cu nanocrystal grains are controlled by adjusting experimental parameters. The relationship between nanocrystal floating gate micro-structure and its charge storage capability is also discussed theoretically.

Effect of Nano Silver Modification on the Dielectric Properties of Ag@TiO_(2)/PVDF Composites

To get a dielectric material with a high dielectric permittivity and suppressed dielectric loss,nano-Ag with a particle size of 20 nm and Ag@TiO_(2)core-shell particles with diameters of approximately 70-120 nm were embedded in polyvinylidene fluoride(PVDF)to fabricate nano-Ag/Ag@TiO_(2)/PVDF composites.After being modified by nano-Ag with 3 vol%optimal amount,the relative permittivity(ε_r)at 100 Hz of 50 vol%Ag@TiO_(2)/PVDF composites was 61,and the dielectric loss can be suppressed to 0.04,almost 96.4%lower than that of unmodified composites,and a higher frequency stability of bothε_r and loss has also been found.The underlying mechanism of the reduced loss was attributed to Maxwell-Wagner polarization and the Coulomb blockade effect caused by the introduction of a small amount of nano-Ag,which will block the movement of electrons between metal nanoparticles and composites.The space charge polarization and conductance loss are weakened at lower and higher Ag@TiO_(2)filling ratios,respectively,thus leading to a very low loss of the composites.

Synergetic protective effects of combined blockade by two kinds of autolesion mediator receptor on neurological function after cervical cord injury

Abstract Objective To investigate the effects of combined blockade by platelet activating factor (PAF) receptor antagonist BN 52021 in combination with opiate receptor antagonist naloxone on neurological function and neurological tissue damage after cervical cord injury. Methods Spinal cord contusion at C 6 segment was made with Allen method in cats, which were randomly divided into four groups: saline control group; BN 52021 group; naloxone group; and combined treatment group with BN 52021 and naloxone. Alteration of cervical cord blood flow, blood barrier permeability of the spinal cord, cervical cord tissue pathology and neurological functional scores were studied after experimental cervical cord injury. Results The animals treated with BN 52021 or naloxone had significantly better functional scores than saline controls 6 weeks after injury (P<0.05). Moreover, the combined treatment showed significantly better neurologic recovery than either naloxone or BN 52021 treated animals (P<0.05). The other indexes in combined treatment animals were also superior to those in naloxone or BN 52021 treated animals. Conclusions Combined blockade by two kinds of autolesion mediator receptor can more effectively inhibit secondary damage production and development after cervical cord injury and improve neurologic function.

COULOMB BLOCKADE EFFECT IN SELF-ASSEMBLED GOLD QUANTUM DOTS

Nanometer-scale Au quantum dots have been assembled on SiO2 by controlling the reaction of raw materials to form a citrate Au sol and an aminosilane/dithiol-treated patterned Si wafer. The detailed formation mechanism has been studied. Three gold colloidal particles (15 nm), aligned in a chain to form a one-dimensional current path, was bridged across an 80-nm gap between source and drain metal electrodes. The device exhibited a Coulomb blockade effect at 33 K.

Buffer-atom-mediated quantum logic gates with off-resonant modulated driving

Connectivity of two-qubit logic gates plays a crucial and indispensable role in quantum computation research.For the cold atom qubit platform,while the two-qubit Rydberg blockade gate has recently made rapid experimental progress,a pressing challenge is to improve connectivity in pursuit of genuine scalability without sacrificing speed or fidelity.A significant advancement in this direction can be achieved by introducing an extra buffer atom to extend the two-qubit gate beyond purely nearest-neighbor two-body interactions.The buffer atom couples with the two qubit atoms through nearest-neighbor interactions,even though the qubit atoms do not directly exert any physical influence on each other.The established method of off-resonant modulated driving(ORMD)is not only convenient but also lays the groundwork for this latest development.Although the atomic linkage structure here exhibits more complex interactions compared to previous two-body systems,the population can satisfactorily return to the ground state after the ground-Rydberg transition with a properly designed modulation waveform.This can be achieved through one-photon and two-photon ground-Rydberg transitions in common practices.Furthermore,with buffer atom relay or similar structures,it is possible to realize a two-qubit entangling gate between two distant qubit atoms.In addition to demonstrating that such solutions are feasible,the representative modulation patterns are analyzed,showcasing the versatility of buffer-atom-mediated two-qubit gates.From a broader perspective,these efforts enhance the resemblance between the cold atom qubit platform and the superconducting qubit system,with the buffer atom functioning like wires and junctions.

Theoretical investigation on tunneling magnetoresistance in ferromagnetic/anti-ferromagnetic core/shell system

Based on Monte Carlo simulations,the effect of structural configuration on the hysteresis behavior and tunneling magnetoresistance(TMR) of composite nanoparticles with ferromagnetic(FM) core/anti-ferromagnetic(AFM) shell is investigated.The simulated results indicate that the coercive field(H c) of composites increases with the decreasing ratio of core-radius(r core) to shell-radius(r shell).When the ratio of r shell to r core is approaching 4:3,H c decreases with increasing AFM thickness.In addition,TMR is found to increase with the decreasing ratio of r core to r shell,resulting from the enhancement of resistance changes in disordered AFM shell.