Recent interesting articles

Quantum technology is maturing to the point where quantum devices, such as quantum communication systems, quantum random number generators and quantum simulators may be built with capabilities exceeding classical computers. A quantum annealer, in particular, solves optimization problems by evolving a known initial configuration at non-zero temperature towards the ground state of a Hamiltonian encoding a given problem. Here, we present results from tests on a 108 qubit D-Wave One device based on superconducting flux qubits. By studying correlations we find that the device performance is inconsistent with classical annealing or that it is governed by classical spin dynamics. In contrast, we find that the device correlates well with simulated quantum annealing. We find further evidence for quantum annealing in the form of small-gap avoided level crossings characterizing the hard problems. To assess the computational power of the device we compare it against optimized classical algorithms.

Nature Physics 10, 218–224 (2014) doi:10.1038/nphys2900

http://www.nature.com/nphys/journal/v10/n3/full/nphys2900.html

Electrons go ballistic

'Juan José Palacios'

A recent experiment shows that graphene nanoribbons can be grown to be perect conductors where electrons travel long distances without coming across a single obstacle.

Nature Physics 10, 182–183 (2014) doi:10.1038/nphys2909

http://www.nature.com/nphys/journal/v10/n3/full/nphys2909.html#access

Quantum droplets of electrons and holes

'A. E. Almand-Hunter, H. Li, S. T. Cundiff, M. Mootz, M. Kira & S. W. Koch'

Interacting many-body systems are characterized by stable configurations of objects—ranging from elementary particles to cosmological formations1, 2, 3—that also act as building blocks for more complicated structures. It is often possible to incorporate interactions in theoretical treatments of crystalline solids by introducing suitable quasiparticles that have an effective mass, spin or charge4, 5 which in turn affects the material’s conductivity, optical response or phase transitions2, 6, 7. Additional quasiparticle interactions may also create strongly correlated configurations yielding new macroscopic phenomena, such as the emergence of a Mott insulator8, superconductivity or the pseudogap phase of high-temperature superconductors9, 10, 11. In semiconductors, a conduction-band electron attracts a valence-band hole (electronic vacancy) to create a bound pair, known as an exciton12, 13, which is yet another quasiparticle. Two excitons may also bind together to give molecules, often referred to as biexcitons14, and even polyexcitons may exist15, 16. In indirect-gap semiconductors such as germanium or silicon, a thermodynamic phase transition may produce electron–hole droplets whose diameter can approach the micrometre range17, 18. In direct-gap semiconductors such as gallium arsenide, the exciton lifetime is too short for such a thermodynamic process. Instead, different quasiparticle configurations are stabilized dominantly by many-body interactions, not by thermalization. The resulting non-equilibrium quantum kinetics is so complicated that stable aggregates containing three or more Coulomb-correlated electron–hole pairs remain mostly unexplored. Here we study such complex aggregates and identify a new stable configuration of charged particles that we call a quantum droplet. This configuration exists in a plasma and exhibits quantization owing to its small size. It is charge neutral and contains a small number of particles with a pair-correlation function that is characteristic of a liquid. We present experimental and theoretical evidence for the existence of quantum droplets in an electron–hole plasma created in a gallium arsenide quantum well by ultrashort optical pulses.

Nature 506, 471–475 (27 February 2014) doi:10.1038/nature12994

http://www.nature.com/nature/journal/v506/n7489/full/nature12994.html

Febr. 1. - Febr. 21. (2014)

Assorted by: Fülöp Bálint

Nanowire section (InAs, InSb)

Magnetotransport Subband Spectroscopy in InAs Nanowires

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.076801

Controlled Synthesis of Phase-Pure InAs Nanowires on Si(111) by Diminishing the Diameter to 10 nm

http://pubs.acs.org/doi/abs/10.1021/nl4040847

Phase Separation in Single InxGa1–xN Nanowires Revealed through a Hard X-ray Synchrotron Nanoprobe

http://pubs.acs.org/doi/abs/10.1021/nl4042752

Mobility Enhancement by Sb-mediated Minimisation of Stacking Fault Density in InAs Nanowires Grown on Silicon

http://pubs.acs.org/doi/abs/10.1021/nl5001554

Strong Terahertz Emission and Its Origin from Catalyst-Free InAs Nanowire Arrays

http://pubs.acs.org/doi/abs/10.1021/nl404737r

Long Term Stability of Nanowire Nanoelectronics in Physiological Environments

http://pubs.acs.org/doi/abs/10.1021/nl500070h

Graphene section

Electron–Phonon Interactions and the Intrinsic Electrical Resistivity of Graphene

http://pubs.acs.org/doi/abs/10.1021/nl402696q

Graphene Oxide-Based Carbon Interconnecting Layer for Polymer Tandem Solar Cells

http://pubs.acs.org/doi/abs/10.1021/nl4046284

Relaxation of optically excited carriers in graphene: Anomalous diffusion and Lévy flights

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.075414

Quantum corrections to thermopower and conductivity in graphene

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.075411

Quantum phase transitions into Kondo states in bilayer graphene

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.081101

Quantum Search on Graphene Lattices

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.070504

High-Contrast Terahertz Wave Modulation by Gated Graphene Enhanced by Extraordinary Transmission through Ring Apertures

http://pubs.acs.org/doi/abs/10.1021/nl4041274

Transport Measurement of Landau Level Gaps in Bilayer Graphene with Layer Polarization Control

http://pubs.acs.org/doi/abs/10.1021/nl4043399

Common Origin of Green Luminescence in Carbon Nanodots and Graphene Quantum Dots

http://pubs.acs.org/doi/abs/10.1021/nn500368m

Self-Organized Platinum Nanoparticles on Freestanding Graphene

http://pubs.acs.org/doi/abs/10.1021/nn406394f

Others (MCBJ, AFM, Majorana, QD, etc.)

Auger-Assisted Electron Transfer from Photoexcited Semiconductor Quantum Dots

http://pubs.acs.org/doi/abs/10.1021/nl4041687

Hot-Electron Photodetection with a Plasmonic Nanostripe Antenna

http://pubs.acs.org/doi/abs/10.1021/nl4044373

Electronic states of wires and slabs of topological insulators: Quantum Hall effects and edge transport

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.085305

Annihilation of Colliding Bogoliubov Quasiparticles Reveals their Majorana Nature

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.070604

Signatures of Majorana fermions in topological insulator Josephson junction devices

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.075106

Electrochemical Charge-Transfer Resistance in Carbon Nanotube Composites

http://pubs.acs.org/doi/abs/10.1021/nl404349g

Flexible Power Fabrics Made of Carbon Nanotubes for Harvesting Thermoelectricity

http://pubs.acs.org/doi/abs/10.1021/nn405893t

Just for fun

Synthetic Antiferromagnetic Nanoparticles as Potential Contrast Agents in MRI

http://pubs.acs.org/doi/abs/10.1021/nn406158h

Fully Solution-Processed Semitransparent Organic Solar Cells with a Silver Nanowire Cathode and a Conducting Polymer Anode

http://pubs.acs.org/doi/abs/10.1021/nn406672n

Using Room Temperature Current Noise To Characterize Single Molecular Spectra

http://pubs.acs.org/doi/abs/10.1021/nn404526w

Laser Damage Helps the Eavesdropper in Quantum Cryptography

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.070503

A New Type of Porous Graphite Foams and Their Integrated Composites with Oxide/Polymer Core/Shell Nanowires for Supercapacitors: Structural Design, Fabrication, and Full Supercapacitor Demonstrations

http://pubs.acs.org/doi/abs/10.1021/nl5001778

Ultrafast Modulation of the Plasma Frequency of Vertically Aligned Indium Tin Oxide Rods

http://pubs.acs.org/doi/abs/10.1021/nl4028044

A bulk graphene mimic

http://www.nature.com/nature/journal/v506/n7488/full/506269d.html

Quantum information: Strength of weak measurementsQuantum information: Strength of weak measurements

The back-action of a weak measurement on the electron spin of a nitrogen–vacancy centre in diamond can be used to steer the associated nuclear spin towards a desired state.

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys2908.html

Not so neutral

Switzerland’s science landscape is under threat after a narrow majority of citizens voted for tighter immigration rules that could restrict the number of foreign scientists who work in the country.

http://www.nature.com/news/not-so-neutral-1.14725

Astronomy: Death of a comet

Before it shattered near the Sun, Comet ISON became a scientific celebrity. Now researchers are trying to piece together its lessons.

http://www.nature.com/news/astronomy-death-of-a-comet-1.14741

Recent interesting articles

From NanoWiki

Contents

Febr. 22. - Márc. 3. (2014)

Febr. 1. - Febr. 21. (2014)

Nanowire section (InAs, InSb)

Graphene section

Others (MCBJ, AFM, Majorana, QD, etc.)

Just for fun

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