Physical Review Letters

Xu, Xiao-Qiang ; Han, Jung Hoon

doi: 10.1103/PhysRevLett.107.200401pmid: 22181715

We examine the combined effects of Rashba spin-orbit (SO) coupling and rotation on trapped spinor Bose-Einstein condensates. The nature of single particle states is thoroughly examined in the Landau level basis and is shown to support the formation of a half-quantum vortex. In the presence of weak s -wave interactions, the ground state at strong SO coupling develops ringlike structures with domains whose number shows step behavior with increasing rotation. For the fast rotation case, the vortex pattern favors a triangular lattice, accompanied by density depletion in the central region and a weakened Skyrmionic character as the SO coupling is enhanced. Giant vortex formation is facilitated when SO coupling and rotation are both strong.

Toudic, B; Lefort, R; Ecolivet, C; Guérin, L; Currat, R; Bourges, P; Breczewski, T

doi: 10.1103/PhysRevLett.107.205502pmid: 22181743

Aperiodic crystals which are long range ordered materials present original dynamics features due to the lack of translational symmetry formally implying the nonvalidity of the Brillouin zone concept. This Letter reports the observation by neutron scattering of an overdamped acousticlike mode at a Bragg peak position in a n -alkane–urea inclusion crystal. This result implies the existence of a gap in the dispersion branch. The gap and anomalous damping of these collective modes are discussed in terms of specific dynamics and interaction in aperiodic materials.

Chambers, S. A; Qiao, L. A; Droubay, T. C; Kaspar, T. C; Arey, B. W; Sushko, P. V

doi: 10.1103/PhysRevLett.107.206802pmid: 22181755

Core-level and valence-band x-ray photoemission spectra measured for molecular-beam-epitaxy-grown LaCrO 3 / SrTiO 3 ( 001 ) yield band offsets and potential gradients within the LaCrO 3 sufficient to trigger an electronic reconstruction to alleviate the polarity mismatch. Yet, the interface is insulating. Based on first principles calculations, we attribute this unexpected result to interfacial cation mixing combined with charge redistribution within CrO 2 layers, enabled by low-lying d states within LaCrO 3 , which suppresses an electronic reconstruction.

Aaltonen, T; Álvarez González, B; Amerio, S; Amidei, D; Anastassov, A; Annovi, A; Antos, J; Apollinari, G; Appel, J. A; Apresyan, A. A; Arisawa, T. A; Artikov, A. A; Asaadi, J. A; Ashmanskas, W. A; Auerbach, B. A; Aurisano, A. A;

von Stecher, Javier

doi: 10.1103/PhysRevLett.107.200402pmid: 22181716

We explore the properties of weakly bound bosonic states in the strongly interacting regime. Combining a correlated-Gaussian basis set expansion with a complex-scaling method, we extract the energies and structural properties of bosonic cluster states with N ≤ 6 for different two-body potentials. The identification of five- and six-body resonances attached to the first-excited-Efimov trimer provides strong support to the premise of Efimov universality in bosonic systems. Our study also reveals a rich structure of bosonic cluster states. Besides the lowest cluster states that behave as bosonic droplets, we identify cluster states weakly bound to one or two atoms forming effective cluster-atom dimers and cluster-atom-atom “trimers.” The experimental signatures of these cluster states are discussed.

Novitsky, Andrey ; Qiu, Cheng-Wei ; Wang, Haifeng

doi: 10.1103/PhysRevLett.107.203601pmid: 22181730

Usually a light beam pushes a particle when the photons act upon it. We investigate the optical forces by nonparaxial gradientless beams and find that the forces can drag suitable particles all the way towards the light source. The major criterion of realizing the backward dragging force is the strong nonparaxiality of the light beam, which contributes to the pulling force owing to momentum conservation. The nonparaxiality of the Bessel beam can be manipulated to possess a dragging force along both the radial longitudinal directions, i.e., a “tractor beam” with stable trajectories is achieved.

Zhao, H. B; Talbayev, D. B; Ma, X. B; Ren, Y. H; Venimadhav, A. H; Li, Qi H; Lüpke, G. H

doi: 10.1103/PhysRevLett.107.207205pmid: 22181766

Pronounced spin precessions are observed in a geometry with negligible canting of the magnetization in ferromagnetic La 0.67 Ca 0.33 MnO 3 thin films using the time-resolved magneto-optical Kerr effect. The precession amplitude monotonically decreases with increasing field, indicating that the coherent spin rotation may be triggered by a transient exchange field and not by demagnetization and/or anisotropy field modulation. We attribute the transient exchange field to emergent antiferromagnetic interactions due to charge transfer and modification of the kinetic energy of e g electrons under optical excitation.

Trojnar, A. H; Korkusiński, M. H; Kadantsev, E. S; Hawrylak, P. S; Goryca, M. S; Kazimierczuk, T. S; Kossacki, P. S; Wojnar, P. S; Potemski, M. S

doi: 10.1103/PhysRevLett.107.207403pmid: 22181774

We show theoretically and experimentally the existence of a new quantum-interference effect between the electron-hole interactions and the scattering by a single Mn impurity. The theoretical model, including electron–valence-hole correlations, the short- and long-range exchange interaction of a Mn ion with the heavy hole and with electron and anisotropy of the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots with single magnetic ions. We show how the design of the electronic levels of a quantum dot enables the design of an exciton, control of the quantum interference, and hence engineering of light-Mn interaction.

Miyata, Atsuhiko ; Ueda, Hiroaki ; Ueda, Yutaka ; Sawabe, Hironobu ; Takeyama, Shojiro

doi: 10.1103/PhysRevLett.107.207203pmid: 22181764

The Faraday rotation and magneto-optical absorption spectral measurements were conducted to reveal the full-magnetization process and map out a magnetic phase diagram of a typical geometrical frustrated magnet, ZnCr 2 O 4 , by using the electro-magnetic flux compression method in ultrahigh magnetic fields up to 600 T. A fully polarized ferromagnetic phase is observed in which the absorption spectra associated with an exciton-magnon-phonon transition disappears. Furthermore, prior to the fully polarized ferromagnetic phase above 410 T, we found a novel magnetic phase above 350 T at 4.6 K followed by a canted 3 ∶ 1 phase.

Ramazanoglu, M; Laver, M; Ratcliff, W; Watson, S. M; Chen, W. C; Jackson, A. C; Kothapalli, K. C; Lee, Seongsu C; Cheong, S.-W. C; Kiryukhin, V. C

doi: 10.1103/PhysRevLett.107.207206pmid: 22181767

Polarized small-angle neutron scattering studies of single-crystalline multiferroic BiFeO 3 reveal a long-wavelength spin density wave generated by ∼ 1 ° spin canting of the spins out of the rotation plane of the antiferromagnetic cycloidal order. This signifies weak ferromagnetism within mesoscopic regions of dimension 0.03 microns along ( 1 1 ¯ 0 ) , to several microns along (111), confirming a long-standing theoretical prediction. The average local magnetization is 0.06 μ B / Fe . Our results provide an indication of the intrinsic macroscopic magnetization to be expected in ferroelectric BiFeO 3 thin films under strain, where the magnetic cycloid is suppressed.