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Jing-Yuan Chen, Jun Ho Son, Chao Wang, S Raghu
The idea of statistical transmutation plays a crucial role in descriptions of the fractional quantum Hall effect. However, a recently conjectured duality between a critical boson and a massless two-component Dirac fermion extends this notion to gapless systems. This duality sheds light on highly nontrivial problems such as the half-filled Landau level, the superconductor-insulator transition, and surface states of strongly coupled topological insulators. Although this boson-fermion duality has undergone many consistency checks, it has remained unproven...
January 5, 2018: Physical Review Letters
Cătălin Paşcu Moca, Christophe Mora, Ireneusz Weymann, Gergely Zaránd
We construct a Fermi liquid theory to describe transport in a superconductor-quantum dot-normal metal junction close to the singlet-doublet (parity changing) transition of the dot. Though quasiparticles do not have a definite charge in this chargeless Fermi liquid, in the case of particle-hole symmetry, a mapping to the Anderson model unveils a hidden U(1) symmetry and a corresponding pseudocharge. In contrast to other correlated Fermi liquids, the back scattering noise reveals an effective charge equal to the charge of Cooper pairs, e^{*}=2e...
January 5, 2018: Physical Review Letters
N M Gergs, S A Bender, R A Duine, D Schuricht
We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state...
January 5, 2018: Physical Review Letters
Timo Schumann, Luca Galletti, David A Kealhofer, Honggyu Kim, Manik Goyal, Susanne Stemmer
The magnetotransport properties of epitaxial films of Cd_{3}As_{2}, a paradigm three-dimensional Dirac semimetal, are investigated. We show that an energy gap opens in the bulk electronic states of sufficiently thin films and, at low temperatures, carriers residing in surface states dominate the electrical transport. The carriers in these states are sufficiently mobile to give rise to a quantized Hall effect. The sharp quantization demonstrates surface transport that is virtually free of parasitic bulk conduction and paves the way for novel quantum transport studies in this class of topological materials...
January 5, 2018: Physical Review Letters
Yang Liu, Xiao Yuan, Ming-Han Li, Weijun Zhang, Qi Zhao, Jiaqiang Zhong, Yuan Cao, Yu-Huai Li, Luo-Kan Chen, Hao Li, Tianyi Peng, Yu-Ao Chen, Cheng-Zhi Peng, Sheng-Cai Shi, Zhen Wang, Lixing You, Xiongfeng Ma, Jingyun Fan, Qiang Zhang, Jian-Wei Pan
Quantum mechanics provides the means of generating genuine randomness that is impossible with deterministic classical processes. Remarkably, the unpredictability of randomness can be certified in a manner that is independent of implementation devices. Here, we present an experimental study of device-independent quantum random number generation based on a detection-loophole-free Bell test with entangled photons. In the randomness analysis, without the independent identical distribution assumption, we consider the worst case scenario that the adversary launches the most powerful attacks against the quantum adversary...
January 5, 2018: Physical Review Letters
Michael Klaiber, Karen Z Hatsagortsyan, Christoph H Keitel
A new pathway of strong-laser-field-induced ionization of an atom is identified which is based on recollisions under the tunneling barrier. With an amended strong-field approximation, the interference of the direct and the under-the-barrier recolliding quantum orbits are shown to induce a measurable shift of the peak of the photoelectron momentum distribution. The scaling of the momentum shift is derived relating the momentum shift to the tunneling delay time according to the Wigner concept. This allows us to extend the Wigner concept for the quasistatic tunneling time delay into the nonadiabatic domain...
January 5, 2018: Physical Review Letters
Zhoushen Huang, W Zhu, Daniel P Arovas, Jian-Xin Zhu, Alexander V Balatsky
We show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z_{2} topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement...
January 5, 2018: Physical Review Letters
Peter Kaufmann, Timm F Gloger, Delia Kaufmann, Michael Johanning, Christof Wunderlich
A promising scheme for building scalable quantum simulators and computers is the synthesis of a scalable system using interconnected subsystems. A prerequisite for this approach is the ability to faithfully transfer quantum information between subsystems. With trapped atomic ions, this can be realized by transporting ions with quantum information encoded into their internal states. Here, we measure with high precision the fidelity of quantum information encoded into hyperfine states of a ^{171}Yb^{+} ion during ion transport in a microstructured Paul trap...
January 5, 2018: Physical Review Letters
M Klaas, H Flayac, M Amthor, I G Savenko, S Brodbeck, T Ala-Nissila, S Klembt, C Schneider, S Höfling
We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor microcavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasicondensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set...
January 5, 2018: Physical Review Letters
Krzysztof Jachymski, Tomasz Wasak, Zbigniew Idziaszek, Paul S Julienne, Antonio Negretti, Tommaso Calarco
Feshbach resonances, which allow for tuning the interactions of ultracold atoms with an external magnetic field, have been widely used to control the properties of quantum gases. We propose a scheme for using scattering resonances as a probe for external fields, showing that by carefully tuning the parameters it is possible to reach a 10^{-5}  G (or nT) level of precision with a single pair of atoms. We show that, for our collisional setup, it is possible to saturate the quantum precision bound with a simple measurement protocol...
January 5, 2018: Physical Review Letters
T P Xiong, L L Yan, F Zhou, K Rehan, D F Liang, L Chen, W L Yang, Z H Ma, M Feng, V Vedral
Most nonequilibrium processes in thermodynamics are quantified only by inequalities; however, the Jarzynski relation presents a remarkably simple and general equality relating nonequilibrium quantities with the equilibrium free energy, and this equality holds in both the classical and quantum regimes. We report a single-spin test and confirmation of the Jarzynski relation in the quantum regime using a single ultracold ^{40}Ca^{+} ion trapped in a harmonic potential, based on a general information-theoretic equality for a temporal evolution of the system sandwiched between two projective measurements...
January 5, 2018: Physical Review Letters
A A Burkov
We demonstrate that, apart from the chiral anomaly, Dirac semimetals possess another quantum anomaly, which we call the mirror anomaly and which manifests in a singular response of the Dirac semimetal to an applied magnetic field. Namely, the anomalous Hall conductivity exhibits step-function singularities when the field is rotated. We show that this phenomenon is closely analogous to the parity anomaly of (2+1)-dimensional Dirac fermions, but with mirror symmetry, which we demonstrate emerges near any Dirac point at a time reversal invariant momentum, replacing the parity symmetry...
January 5, 2018: Physical Review Letters
Insun Jo, Hao Deng, Yang Liu, L N Pfeiffer, K W West, K W Baldwin, M Shayegan
We study a bilayer GaAs hole system that hosts two distinct many-body phases at low temperatures and high perpendicular magnetic fields. The higher-density (top) layer develops a Fermi sea of composite fermions (CFs) in its half-filled lowest Landau level, while the lower-density (bottom) layer forms a Wigner crystal (WC) as its filling becomes very small. Owing to the interlayer interaction, the CFs in the top layer feel the periodic Coulomb potential of the WC in the bottom layer. We measure the magnetoresistance of the top layer while changing the bottom-layer density...
January 5, 2018: Physical Review Letters
Marsel Z Shafikov, Alfiya Suleymanova, Alexander Schinabeck, Hartmut Yersin
The di-nuclear Ag(I) complex has been designed to show thermally activated delayed fluorescence (TADF) оf high efficiency. Strongly electron-donating terminal ligands are introduced to destabilize the d-orbitals of the Ag+ ions. Consequently, the orbitals distinctly contribute to the HOMO, whereas the LUMO is localized on the bridging ligand. This ensures charge transfer character of the lowest excited singlet S1 and triplet T1 state. Accordingly, a small energy gap ΔE(S1─T1) is obtained, being essential for TADF behavior...
January 19, 2018: Journal of Physical Chemistry Letters
Sankar Raman Vaikuntam, Klaus Werner Stöckelhuber, Eshwaran Subramani Bhagavatheswaran, Sven Wiessner, Ulrich Scheler, Kay Saalwaechter, Petr Formanek, Gert Heinrich, Amit Das
A sol-gel transformation of liquid silica precursor to solid silica particles was carried out in a one pot synthesis way where a solution of styrene butadiene elastomer (S-SBR) was present. The composites, thus produced, offered remarkable improvements of mechanical and dynamic mechanical performances as compared with precipitated silica. The morphological analysis reveals that the alkoxy-based silica particles resemble a raspberry structure when the synthesis of the silica was carried out in presence of polymer molecules and represent a much more open silica-network structure...
January 19, 2018: Journal of Physical Chemistry. B
Xiaoyu Zhao, Xiaoyu Song, Yang Li, Ze Chang, Long Chen
Metal-organic frameworks (MOFs) have emerged as promising light-harvesting platforms for energy transfer materials. However, the targeted construction of MOFs with desirable photophysical properties and pore structures is still a challenge. Herein, 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl)ethene (tppe) is selected as ligand for the construction of light-harvesting MOFs due to its highly emissive and rigid backbone, which could benefit the light-harvesting performance of the MOFs. Three MOFs (MOFs 1-3) were obtained based on different metal centers (Zn2+ and Cd2+) and carboxylate building blocks...
January 19, 2018: ACS Applied Materials & Interfaces
Xin Hai, Zhiyong Guo, Xin Lin, Xuwei Chen, Jian-Hua Wang
A fluorescent probe TPA@GQDs is fabricated by the conjugation of terephthalic acid (TPA) on the surface of graphene quantum dots (GQDs). The TPA@GQDs probe not only owns favorable dispersibility, but also exhibits excellent fluorescence stability over wide pH range and high ionic strength, and favorable anti-photobleaching ability. The great fluorescence enhancement of TPA@GQDs induced by the reaction between TPA and hydroxyl radical makes the TPA@GQDs a powerful probe for the sensitive assay of hydroxyl radical, giving rise to a detection limit low down to 12 nmol L-1...
January 19, 2018: ACS Applied Materials & Interfaces
Paul Kuyanov, Simon McNamee, Ray R LaPierre
We report the structural, optical and electrical properties of GaAs quantum dots (QDs) embedded along GaP nanowires. The GaP nanowires contained p-i-n junctions with 15 GaAs QDs within the intrinsic region. The nanowires were grown by molecular beam epitaxy using the self-assisted vapor-liquid-solid process. The crystal structure of the NW alternated between twinned ZB and WZ as the composition along the NW alternated between the GaP barriers and the GaAs QDs, respectively, leading to a polytypic structure with a periodic modulation of the NW sidewall facets...
January 19, 2018: Nanotechnology
Chong Chen, Stuart N Holmes, Ian Farrer, Harvey E Beere, David A Ritchie
InGaAs based devices are great complements to silicon for CMOS, as they provide an increased carrier saturation velocity, lower operating voltage and reduced power dissipation. In this work we show that In0.75Ga0.25As quantum wells with a high mobility, 15 000 to 20 000 cm2/V.s at ambient temperature, show an InAs-like phonon with an energy of 28.8 meV, frequency of 232 cm-1 that dominates the polar-optical mode scattering from ∼ 70 K to 300 K. The optical phonon frequency is insensitive to the carrier density modulated with a surface gate or LED illumination...
January 19, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Gang Wang, Qinglei Guo, Da Chen, Zhiduo Liu, Xiaohu Zheng, Anli Xu, Siwei Yang, Guqiao Ding
Recently, the biomass "bottom-up" approach for the synthesis of graphene quantum dots have attracted broad interest because of the outstanding features, including low-cost, rapid and environmentally friendly nature. However, the low crystalline quality of products, substitutional doping with heteroatoms in lattice and ambiguous reaction mechanism strongly challenge the further development of this technique. Herein, we proposed a facile and effective strategy to prepare controllable sulfur (S) doping in graphene quantum dots, occurring in a lattice substitution manner, by hydrothermal treatment of durian with platinum catalyst...
January 19, 2018: ACS Applied Materials & Interfaces
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