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Physical Review Letters

S Gandolfi, H-W Hammer, P Klos, J E Lynn, A Schwenk
We present quantum Monte Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next-to-next-to-leading order in chiral effective field theory. The energy and radial densities for these systems are calculated in different external Woods-Saxon potentials. We assume that their extrapolation to zero external-potential depth provides a quantitative estimate of three- and four-neutron resonances. The validity of this assumption is demonstrated by benchmarking with an exact diagonalization in the two-body case...
June 9, 2017: Physical Review Letters
Chengjie Xia, Jindong Li, Binquan Kou, Yixin Cao, Zhifeng Li, Xianghui Xiao, Yanan Fu, Tiqiao Xiao, Liang Hong, Jie Zhang, Walter Kob, Yujie Wang
Recent diffraction experiments on metallic glasses have unveiled an unexpected noncubic scaling law between density and average interatomic distance, which led to the speculation of the presence of fractal glass order. Using x-ray tomography we identify here a similar noncubic scaling law in disordered granular packing of spherical particles. We find that the scaling law is directly related to the contact neighbors within the first nearest neighbor shell, and, therefore, is closely connected to the phenomenon of jamming...
June 9, 2017: Physical Review Letters
P Adamson, L Aliaga, D Ambrose, N Anfimov, A Antoshkin, E Arrieta-Diaz, K Augsten, A Aurisano, C Backhouse, M Baird, B A Bambah, K Bays, B Behera, S Bending, R Bernstein, V Bhatnagar, B Bhuyan, J Bian, T Blackburn, A Bolshakova, C Bromberg, J Brown, G Brunetti, N Buchanan, A Butkevich, V Bychkov, M Campbell, E Catano-Mur, S Childress, B C Choudhary, B Chowdhury, T E Coan, J A B Coelho, M Colo, J Cooper, L Corwin, L Cremonesi, D Cronin-Hennessy, G S Davies, J P Davies, P F Derwent, R Dharmapalan, P Ding, Z Djurcic, E C Dukes, H Duyang, S Edayath, R Ehrlich, G J Feldman, M J Frank, M Gabrielyan, H R Gallagher, S Germani, T Ghosh, A Giri, R A Gomes, M C Goodman, V Grichine, R Group, D Grover, B Guo, A Habig, J Hartnell, R Hatcher, A Hatzikoutelis, K Heller, A Himmel, A Holin, J Hylen, F Jediny, M Judah, G K Kafka, D Kalra, S M S Kasahara, S Kasetti, R Keloth, L Kolupaeva, S Kotelnikov, I Kourbanis, A Kreymer, A Kumar, S Kurbanov, K Lang, W M Lee, S Lin, J Liu, M Lokajicek, J Lozier, S Luchuk, K Maan, S Magill, W A Mann, M L Marshak, K Matera, V Matveev, D P Méndez, M D Messier, H Meyer, T Miao, W H Miller, S R Mishra, R Mohanta, A Moren, L Mualem, M Muether, S Mufson, R Murphy, J Musser, J K Nelson, R Nichol, E Niner, A Norman, T Nosek, Y Oksuzian, A Olshevskiy, T Olson, J Paley, P Pandey, R B Patterson, G Pawloski, D Pershey, O Petrova, R Petti, S Phan-Budd, R K Plunkett, R Poling, B Potukuchi, C Principato, F Psihas, A Radovic, R A Rameika, B Rebel, B Reed, D Rocco, P Rojas, V Ryabov, K Sachdev, P Sail, O Samoylov, M C Sanchez, R Schroeter, J Sepulveda-Quiroz, P Shanahan, A Sheshukov, J Singh, J Singh, P Singh, V Singh, J Smolik, N Solomey, E Song, A Sousa, K Soustruznik, M Strait, L Suter, R L Talaga, M C Tamsett, P Tas, R B Thayyullathil, J Thomas, X Tian, S C Tognini, J Tripathi, A Tsaris, J Urheim, P Vahle, J Vasel, L Vinton, A Vold, T Vrba, B Wang, M Wetstein, D Whittington, S G Wojcicki, J Wolcott, N Yadav, S Yang, J Zalesak, B Zamorano, R Zwaska
Results are reported from an improved measurement of ν_{μ}→ν_{e} transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^{20} protons on target, 33 ν_{e} candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_{μ} disappearance data and external constraints from reactor experiments on sin^{2}2θ_{13}, the hypothesis of inverted mass hierarchy with θ_{23} in the lower octant is disfavored at greater than 93% C.L. for all values of δ_{CP}.
June 9, 2017: Physical Review Letters
Günter Kewes, Kathrin Herrmann, Rogelio Rodríguez-Oliveros, Alexander Kuhlicke, Oliver Benson, Kurt Busch
We present a semiclassical analytic model for spherical core-shell surface plasmon lasers. Within this model, we drop the widely used one-mode approximations in favor of fully electromagnetic Mie theory. This allows for incorporation of realistic gain relaxation rates that so far are massively underestimated. Especially, higher order modes can undermine and even reverse the beneficial effects of the strong Purcell effect in such systems. Our model gives a clear view on gain and resonator requirements, as well as on the output characteristics that will help experimenters to design more efficient particle-based spasers...
June 9, 2017: Physical Review Letters
Luca Taddia, Eyal Cornfeld, Davide Rossini, Leonardo Mazza, Eran Sela, Rosario Fazio
Alkaline-earth(-like) atoms, trapped in optical lattices and in the presence of an external gauge field, can form insulating states at given fractional fillings. We will show that, by exploiting these properties, it is possible to realize a topological fractional pump. Our analysis is based on a many-body adiabatic expansion, on simulations with time-dependent matrix product states, and, for a specific form of atom-atom interaction, on an exactly solvable model of fractional pump. The numerical simulations allow us to consider a realistic setup amenable of an experimental realization...
June 9, 2017: Physical Review Letters
P Virtanen, T T Heikkilä
We analyze the statistics of charge and energy currents and spin torque in a metallic nanomagnet coupled to a large magnetic metal via a tunnel contact. We derive a Keldysh action for the tunnel barrier, describing the stochastic currents in the presence of a magnetization precessing with the rate Ω. In contrast to some earlier approaches, our result is valid for an arbitrary ratio of ℏΩ/k_{B}T. We illustrate the use of the action by deriving spintronic fluctuation relations, the quantum limit of pumped current noise, and consider the fluctuations in two specific cases: the situation with a stable precession of magnetization driven by spin transfer torque, and the torque-induced switching between the minima of a magnetic anisotropy...
June 9, 2017: Physical Review Letters
Alexander Rokash, Evgeny Epelbaum, Hermann Krebs, Dean Lee
Recent ab initio lattice studies have found that the interactions between alpha particles (^{4}He nuclei) are sensitive to seemingly minor details of the nucleon-nucleon force, such as interaction locality. In order to uncover the essential physics of this puzzling phenomenon without unnecessary complications, we study a simple model involving two-component fermions in one spatial dimension. We probe the interaction between two bound dimers for several different particle-particle interactions and measure an effective potential between the dimers using external point potentials which act as numerical tweezers...
June 9, 2017: Physical Review Letters
Zizhu Wang, Sukhwinder Singh, Miguel Navascués
We consider the problem of detecting entanglement and nonlocality in one-dimensional (1D) infinite, translation-invariant (TI) systems when just near-neighbor information is available. This issue is deeper than one might think a priori, since, as we show, there exist instances of local separable states (classical boxes) which admit only entangled (nonclassical) TI extensions. We provide a simple characterization of the set of local states of multiseparable TI spin chains and construct a family of linear witnesses which can detect entanglement in infinite TI states from the nearest-neighbor reduced density matrix...
June 9, 2017: Physical Review Letters
Renming Liu, Zhang-Kai Zhou, Yi-Cong Yu, Tengwei Zhang, Hao Wang, Guanghui Liu, Yuming Wei, Huanjun Chen, Xue-Hua Wang
Reaching the quantum optics limit of strong light-matter interactions between a single exciton and a plasmon mode is highly desirable, because it opens up possibilities to explore room-temperature quantum devices operating at the single-photon level. However, two challenges severely hinder the realization of this limit: the integration of single-exciton emitters with plasmonic nanostructures and making the coupling strength at the single-exciton level overcome the large damping of the plasmon mode. Here, we demonstrate that these two hindrances can be overcome by attaching individual J aggregates to single cuboid Au@Ag nanorods...
June 9, 2017: Physical Review Letters
Kai Schlage, Liudmila Dzemiantsova, Lars Bocklage, Hans-Christian Wille, Matthias Pues, Guido Meier, Ralf Röhlsberger
Nuclear resonant x-ray diffraction in grazing incidence geometry is used to determine the lateral magnetic configuration in a one-dimensional lattice of ferromagnetic nanostripes. During magnetic reversal, strong nuclear superstructure diffraction peaks appear in addition to the electronic ones due to an antiferromagnetic order in the nanostripe lattice. We show that the analysis of the angular distribution together with the time dependence of the resonantly diffracted x rays reveals surface spin structures with very high sensitivity...
June 9, 2017: Physical Review Letters
Ilya Svetlizky, Elsa Bayart, Gil Cohen, Jay Fineberg
Frictional resistance to slip, τ, is determined by the real area of contact, A, and the shear strength of the contacts forming the frictional interface. We perform simultaneous high-speed local measurements of τ and A at the tail of propagating rupture fronts. Rate dependence is investigated over 2 orders of magnitude of local slip velocities which reach up to ∼1  m/s. A critical slip velocity is observed that signifies a transition in the frictional behavior: enhanced velocity weakening of A and τ...
June 9, 2017: Physical Review Letters
Patrick Back, Meinrad Sidler, Ovidiu Cotlet, Ajit Srivastava, Naotomo Takemura, Martin Kroner, Atac Imamoğlu
For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 T leads to a near-complete valley polarization of electrons in a MoSe_{2} monolayer with a density 1.6×10^{12}  cm^{-2}; in the absence of exchange interactions favoring single-valley occupancy, a similar degree of valley polarization would have required a pseudospin g factor of 38...
June 9, 2017: Physical Review Letters
Bing He, Liu Yang, Qing Lin, Min Xiao
One of the most fundamental problems in optomechanical cooling is how small the thermal phonon number of a mechanical oscillator can be achieved under the radiation pressure of a proper cavity field. Different from previous theoretical predictions, which were based on an optomechanical system's time-independent steady states, we treat such cooling as a dynamical process of driving the mechanical oscillator from its initial thermal state, due to its thermal equilibrium with the environment, to a stabilized quantum state of higher purity...
June 9, 2017: Physical Review Letters
Xie Zhang, Tilmann Hickel, Jutta Rogal, Jörg Neugebauer
Employing ab initio calculations we demonstrate that the complex structural modulations experimentally observed in ultrathin Fe films on Cu(001) originate from Fe bulk phases that arise under extreme deformations. Specifically, we show that the structural modulations correspond to the motifs observed when transforming fcc Fe to bcc Fe in the Pitsch orientation relationship [(001)_{fcc}||(11[over ¯]0)_{bcc}]. The observed structural equivalence between surface and unstable bulk structures naturally explains the experimentally reported magnetic and structural transitions when going from low (two to four MLs) to intermediate (four to ten MLs) film coverages...
June 9, 2017: Physical Review Letters
Kaveh Ahadi, Susanne Stemmer
We report on a metal-insulator transition (MIT) that is observed in an electron system at the SmTiO_{3}/SrTiO_{3} interface. This MIT is characterized by an abrupt transition at a critical temperature, below which the resistance changes by more than an order of magnitude. The temperature of the transition systematically depends on the carrier density, which is tuned from ∼1×10^{14} to 3×10^{14}  cm^{-2} by changing the SmTiO_{3} thickness. An analysis of the transport properties shows non-Fermi-liquid behavior and mass enhancement as the carrier density is lowered...
June 9, 2017: Physical Review Letters
Henriette Elvang, Callum R T Jones, Stephen G Naculich
Extensions of the photon and graviton soft theorems are derived in 4D local effective field theories with massless particles of arbitrary spin. We prove that effective operators can result in new terms in the soft theorems at subleading order for photons and subsubleading order for gravitons. The new soft terms are unique, and we provide a complete classification of all local operators responsible for such modifications. We show that no local operators can modify the subleading soft graviton theorem. The soft limits are taken in a manifestly on-locus manner using a complex double deformation of the external momenta...
June 9, 2017: Physical Review Letters
Kayleigh Cassella, Eric Copenhaver, Brian Estey, Yanying Feng, Chen Lai, Holger Müller
We report simultaneous conjugate Ramsey-Bordé interferometers with a sample of low-mass (lithium-7) atoms at 50 times the recoil temperature. We optically pump the atoms to a magnetically insensitive state using the 2S_{1/2}-2P_{1/2} line. Fast stimulated Raman beam splitters address a broad velocity class and unavoidably drive two conjugate interferometers that overlap spatially. We show that detecting the summed interference signals of both interferometers, using state labeling, allows recoil measurements and suppression of phase noise from vibrations...
June 9, 2017: Physical Review Letters
V Ros, M Müller
We study the remanent magnetization in antiferromagnetic, many-body localized quantum spin chains, initialized in a fully magnetized state. Its long time limit is an order parameter for the localization transition, which is readily accessible by standard experimental probes in magnets. We analytically calculate its value in the strong-disorder regime exploiting the explicit construction of quasilocal conserved quantities of the localized phase. We discuss analogies in cold atomic systems.
June 9, 2017: Physical Review Letters
Alberto Antonioni, Alessio Cardillo
Despite the large number of studies on synchronization, the hypothesis that interactions bear a cost for involved individuals has seldom been considered. The introduction of costly interactions leads, instead, to the formulation of a dichotomous scenario in which an individual may decide to cooperate and pay the cost in order to get synchronized with the rest of the population. Alternatively, the same individual can decide to free ride, without incurring any cost, waiting for others to get synchronized to his or her state...
June 9, 2017: Physical Review Letters
J Z Zhao, W Fan, M J Verstraete, Z Zanolli, J Fan, X B Yang, H Xu, S Y Tong
No abstract text is available yet for this article.
June 9, 2017: Physical Review Letters
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