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
Szept.5-12.
Tóvári Endre
All-optical control of ferromagnetic thin films and nanostructures
'C-H. Lambert, S. Mangin, B. S. D. Ch. S. Varaprasad, Y. K. Takahashi, M. Hehn, M. Cinchetti, G. Malinowski, K. Hono, Y. Fainman, M. Aeschlimann, E. E. Fullerton'
The interplay of light and magnetism allowed light to be used as a probe of magnetic materials. Now the focus has shifted to use polarized light to alter or manipulate magnetism. Here, we demonstrate optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed and may have a major impact on data memory and storage industries through the integration of optical control of ferromagnetic bits.
http://www.sciencemag.org/content/345/6202/1337
Ultrafast optical control of orbital and spin dynamics in a solid-state defect
'Lee C. Bassett, F. Joseph Heremans, David J. Christle, Christopher G. Yale, Guido Burkard, Bob B. Buckley, David D. Awschalom'
Atom-scale defects in semiconductors are promising building blocks for quantum devices, but our understanding of their material-dependent electronic structure, optical interactions, and dissipation mechanisms is lacking. Using picosecond resonant pulses of light, we study the coherent orbital and spin dynamics of a single nitrogen-vacancy center in diamond over time scales spanning six orders of magnitude. We develop a time-domain quantum tomography technique to precisely map the defect’s excited-state Hamiltonian and exploit the excited-state dynamics to control its ground-state spin with optical pulses alone. These techniques generalize to other optically addressable nanoscale spin systems and serve as powerful tools to characterize and control spin qubits for future applications in quantum technology.
http://www.sciencemag.org/content/345/6202/1333
Environment-assisted quantum control of a solid-state spin via coherent dark states
'Jack Hansom, Carsten H. H. Schulte, Claire Le Gall, Clemens Matthiesen, Edmund Clarke, Maxime Hugues, Jacob M. Taylor & Mete Atatüre'
Understanding the interplay between a quantum system and its environment lies at the heart of quantum science and its applications. So far most efforts have focused on circumventing decoherence induced by the environment by either protecting the system from the associated noise1, 2, 3, 4, 5 or by manipulating the environment directly6, 7, 8, 9. Recently, parallel efforts using the environment as a resource have emerged, which could enable dissipation-driven quantum computation and coupling of distant quantum bits10, 11, 12, 13, 14. Here, we realize the optical control of a semiconductor quantum-dot spin by relying on its interaction with an adiabatically evolving spin environment. The emergence of hyperfine-induced, quasi-static optical selection rules enables the optical generation of coherent spin dark states without an external magnetic field. We show that the phase and amplitude of the lasers implement multi-axis manipulation of the basis spanned by the dark and bright states, enabling control via projection into a spin-superposition state. Our approach can be extended, within the scope of quantum control and feedback15, 16, to other systems interacting with an adiabatically evolving environment.
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3077.html
Graphene nanoribbon heterojunctions
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2014.184.html
Generation and electric control of spin–valley-coupled circular photogalvanic current in WSe2
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2014.183.html
Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures
'A. Mishchenko, J. S. Tu, Y. Cao, R. V. Gorbachev, J. R. Wallbank, M. T. Greenaway, V. E. Morozov, S. V. Morozov, M. J. Zhu, S. L. Wong, F. Withers, C. R. Woods, Y-J. Kim, K. Watanabe, T. Taniguchi, E. E. Vdovin, O. Makarovsky, T. M. Fromhold, V. I. Fal'ko, A. K. Geim, L. Eaves & K. S. Novoselov'
Recent developments in the technology of van der Waals heterostructures1, 2 made from two-dimensional atomic crystals3, 4 have already led to the observation of new physical phenomena, such as the metal–insulator transition5 and Coulomb drag6, and to the realization of functional devices, such as tunnel diodes7, 8, tunnel transistors9, 10 and photovoltaic sensors11. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack12, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers13, 14, 15, 16, 17. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology.
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2014.187.html
Sensitive room-temperature terahertz detection via the photothermoelectric effect in graphene
'Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Mohammad M. Jadidi, Gregory S. Jenkins, Luke O. Nyakiti, Rachael L. Myers-Ward, Shanshan Li, Jun Yan, D. Kurt Gaskill, Thomas E. Murphy, H. Dennis Drew & Michael S. Fuhrer'
Terahertz radiation has uses in applications ranging from security to medicine1. However, sensitive room-temperature detection of terahertz radiation is notoriously difficult2. The hot-electron photothermoelectric effect in graphene is a promising detection mechanism; photoexcited carriers rapidly thermalize due to strong electron–electron interactions3, 4, but lose energy to the lattice more slowly3, 5. The electron temperature gradient drives electron diffusion, and asymmetry due to local gating6, 7 or dissimilar contact metals8 produces a net current via the thermoelectric effect. Here, we demonstrate a graphene thermoelectric terahertz photodetector with sensitivity exceeding 10 V W–1 (700 V W–1) at room temperature and noise-equivalent power less than 1,100 pW Hz–1/2 (20 pW Hz–1/2), referenced to the incident (absorbed) power. This implies a performance that is competitive with the best room-temperature terahertz detectors9 for an optimally coupled device, and time-resolved measurements indicate that our graphene detector is eight to nine orders of magnitude faster than those7, 10. A simple model of the response, including contact asymmetries (resistance, work function and Fermi-energy pinning) reproduces the qualitative features of the data, and indicates that orders-of-magnitude sensitivity improvements are possible.
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2014.182.html
Polycrystalline Graphene with Single Crystalline Electronic Structure
http://pubs.acs.org/doi/abs/10.1021/nl502445j
