Recent interesting articles
From NanoWiki
Nature Nanotechnology last week
Cond-mat Mesoscale and Nanoscale Physics - recent papers Note: all the papers in a certain month can be listed as e.g. http://xxx.lanl.gov/list/cond-mat.mes-hall/1104 , where 11 stands for 2011 and 04 for April.
Link to the archive of this series before 2014
Contents |
Febr. 22. - Márc. 3. (2014)
Assorted by: Magyarkuti András
An antidamping spin–orbit torque originating from the Berry curvature
'H. Kurebayashi, Jairo Sinova, D. Fang, A. C. Irvine, T. D. Skinner, J. Wunderlich, V. Novák, R. P. Campion, B. L. Gallagher, E. K. Vehstedt, L. P. Zârbo, K. Výborný, A. J. Ferguson & T. Jungwirth'
Magnetization switching at the interface between ferromagnetic and paramagnetic metals, controlled by current-induced torques, could be exploited in magnetic memory technologies. Compelling questions arise regarding the role played in the switching by the spin Hall effect in the paramagnet and by the spin–orbit torque originating from the broken inversion symmetry at the interface. Of particular importance are the antidamping components of these current-induced torques acting against the equilibrium-restoring Gilbert damping of the magnetization dynamics. Here, we report the observation of an antidamping spin–orbit torque that stems from the Berry curvature, in analogy to the origin of the intrinsic spin Hall effect. We chose the ferromagnetic semiconductor (Ga,Mn)As as a material system because its crystal inversion asymmetry allows us to measure bare ferromagnetic films, rather than ferromagnetic–paramagnetic heterostructures, eliminating by design any spin Hall effect contribution. We provide an intuitive picture of the Berry curvature origin of this antidamping spin–orbit torque as well as its microscopic modelling. We expect the Berry curvature spin–orbit torque to be of comparable strength to the spin-Hall-effect-driven antidamping torque in ferromagnets interfaced with paramagnets with strong intrinsic spin Hall effect.
Nature Nanotechnology 9, 211–217 (2014) doi:10.1038/nnano.2014.15
http://www.nature.com/nnano/journal/v9/n3/full/nnano.2014.15.html
Evidence for quantum annealing with more than one hundred qubits
'Sergio Boixo, Troels F. Rønnow, Sergei V. Isakov, Zhihui Wang, David Wecker, Daniel A. Lidar, John M. Martinis & Matthias Troyer'
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 perect 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
