Physical Review Letters

Fujita, Katsumasa ; Kobayashi, Minoru ; Kawano, Shogo ; Yamanaka, Masahito ; Kawata, Satoshi

doi: 10.1103/PhysRevLett.99.228105pmid: 18233334

We demonstrate the use of saturated excitation in confocal fluorescence microscopy to improve the spatial resolution. In the proposed technique, we modulate the excitation intensity temporally and detect the harmonic modulation of the fluorescence signal which is caused by the saturated excitation in the center of the laser focus. Theoretical and experimental investigations show that the demodulated fluorescence signal is nonlinearly proportional to the excitation intensity and contributes to improve the spatial resolution in three dimensions beyond the diffraction limit of light.

Serga, A. A; Chumak, A. V; André, A. V; Melkov, G. A; Slavin, A. N; Demokritov, S. O; Hillebrands, B. O

doi: 10.1103/PhysRevLett.99.227202pmid: 18233319

We demonstrate that a microwave signal carried by a packet of dipolar spin waves propagating in a tangentially magnetized magnetic film can be stored in the form of standing dipole-exchange spin-wave modes of the film and can be recovered by means of a double-frequency parametric pumping mechanism. This mechanism is based on the parametric amplification of the standing (thickness) modes of the film by external pumping. The time of recovery, duration, and power of the recovered pulse signal are controlled by the power of the pumping signal.

Vila, Laurent ; Kimura, Takashi ; Otani, YoshiChika

doi: 10.1103/PhysRevLett.99.226604pmid: 18233310

We have studied the evolution of the spin Hall effect (SHE) in the regime where the material size responsible for the spin accumulation is either smaller or larger than the spin diffusion length. Lateral spin valve structures with Pt insertions were successfully used to measure the spin absorption efficiency as well as the spin accumulation in Pt induced through the spin Hall effect. Under a constant applied current the results show a decrease of the spin accumulation signal is more pronounced as the Pt thickness exceeds the spin diffusion length. This implies that the spin accumulation originates from bulk scattering inside the Pt wire and the spin diffusion length limits the SHE. We have also analyzed the temperature variation of the spin Hall conductivity to identify the dominant scattering mechanism.

Blumberg, G; Mialitsin, A; Dennis, B. S; Klein, M. V; Zhigadlo, N. D; Karpinski, J. D

doi: 10.1103/PhysRevLett.99.227002pmid: 18233316

We report observation of Leggett’s collective mode in a multiband MgB 2 superconductor with T c = 39 K arising from the fluctuations in the relative phase between two superconducting condensates. The novel mode is observed by Raman spectroscopy at 9.4 meV in the fully symmetric scattering channel. The observed mode frequency is consistent with theoretical considerations based on first-principles computations.

Chaté, Hugues ; Ginelli, Francesco

doi: 10.1103/PhysRevLett.99.229601pmid: 18233344

A Comment on the Letter by M. Aldana et al. , Phys. Rev. Lett. PRLTAO 0031-9007 98 , 095702 ( 2007 ) 10.1103/PhysRevLett.98.095702 .

Itin, A. P; Watanabe, S. P

doi: 10.1103/PhysRevLett.99.223903pmid: 18233287

We study the dynamics of a two-color photoassociation of atoms into diatomic molecules via nonlinear stimulated Raman adiabatic passage process. The system has a famous counterpart in (linear) quantum mechanics, and has been discussed recently in the context of generalizing the quantum adiabatic theorem to nonlinear systems. Here we use another approach to study adiabaticity and stability in the system: we apply methods of classical Hamiltonian dynamics. We find nonlinear dynamical instabilities, cases of complete integrability, and improved conditions of adiabaticity.

Barci, Daniel G

doi: 10.1103/PhysRevLett.99.228904pmid: N/A

A Reply to the Comment by Yan Levin.

Schull, G; Berndt, R

doi: 10.1103/PhysRevLett.99.226105pmid: 18233303

Long range orientational order within C 60 monolayers on Au(111) is observed with low-temperature scanning tunneling microscopy. A unit cell comprised of 49 molecules which adopt 11 different orientations is found. It can be divided in a faulted and an unfaulted half similar to the ( 7 × 7 ) reconstruction of Si(111). A model is proposed which shows how, through a Moiré-like effect, the substrate induces minute changes in the orientation of the C 60 molecules. Intermolecular interactions are shown to play a major role in stabilizing the superlattice.

Cabello, Adán ; Moreno, Pilar

doi: 10.1103/PhysRevLett.99.220402pmid: 18233265

If n qubits were distributed between 2 parties, which quantum pure states and distributions of qubits would allow all-versus-nothing (or Greenberger-Horne-Zeilinger-like) proofs of Bell’s theorem using only single-qubit measurements? We show a necessary and sufficient condition for the existence of these proofs for any number of qubits, and provide all distinct proofs up to n = 7 qubits. Remarkably, there is only one distribution of a state of n = 4 qubits, and six distributions, each for a different state of n = 6 qubits, which allow these proofs.

Harris, J. G; Nguyen, S. V; Doret, S. C; Ketterle, W. C; Doyle, J. M

doi: 10.1103/PhysRevLett.99.223201pmid: 18233281

Angular momentum changing collisions can be suppressed in atoms whose valence electrons are submerged beneath filled shells of higher principle quantum number. To determine whether spin-exchange collisions are suppressed in these “submerged shell” atoms, we measured collisional rates for six hyperfine states of Mn at T < 1 K . Although the 3 d valence electrons in Mn are submerged beneath a filled 4 s orbital, we find spin-exchange rate coefficients similar to Na and H (both nonsubmerged shell atoms).