Poynor, Adelé ; Hong, Liang ; Robinson, Ian K; Granick, Steve K
doi: 10.1103/PhysRevLett.101.039602pmid: N/A
A Reply to the Comment by Benjamin M. Ocko, Ali Dhinojwala, and Jean Daillant.
Brataas, Arne ; Tserkovnyak, Yaroslav ; Bauer, Gerrit E
doi: 10.1103/PhysRevLett.101.037207pmid: 18764289
The magnetization dynamics of a single domain ferromagnet in contact with a thermal bath is studied by scattering theory. We recover the Landau-Liftshitz-Gilbert equation and express the effective fields and Gilbert damping tensor in terms of the scattering matrix. Dissipation of magnetic energy equals energy current pumped out of the system by the time-dependent magnetization, with separable spin-relaxation induced bulk and spin-pumping generated interface contributions. In linear response, our scattering theory for the Gilbert damping tensor is equivalent with the Kubo formalism.
Cazayous, M; Gallais, Y; Sacuto, A
doi: 10.1103/PhysRevLett.101.037601pmid: 18764295
We unravel the magnon spectra of BiFeO 3 by means of low-energy inelastic light scattering. We show the existence of two species of magnons corresponding to spin wave excitations in and out of the cycloidal plane. These excitations might be interpreted as electromagnon modes. The present observations present an unique opportunity to study the competition between ferroelectric and magnetic orders.
Kolpak, Alexie M; Li, Dongbo M; Shao, Rui M; Rappe, Andrew M; Bonnell, Dawn A
doi: 10.1103/PhysRevLett.101.036102pmid: 18764267
We report a series of new surface reconstructions on BaTiO 3 ( 001 ) as a function of environmental conditions, determined via scanning tunneling microscopy and low energy electron diffraction. Using density functional theory calculations and thermodynamic modeling, we construct a surface phase diagram and determine the atomic structures of the thermodynamically stable phases. Excellent agreement is found between the predicted phase diagram and experiment. The results enable prediction of surface structures and properties under the entire range of accessible environmental conditions.
Hew, W. K; Thomas, K. J; Pepper, M. J; Farrer, I. J; Anderson, D. J; Jones, G. A; Ritchie, D. A
doi: 10.1103/PhysRevLett.101.036801pmid: 18764272
When a quantum wire is weakly confined, a conductance plateau appears at e 2 / h with decreasing carrier density in zero magnetic field accompanied by a gradual suppression of the 2 e 2 / h plateau. Applying an in-plane magnetic field B ∥ does not alter the value of this quantization; however, the e 2 / h plateau weakens with increasing B ∥ up to 9 T, and then strengthens on further increasing B ∥ , which also restores the 2 e 2 / h plateau. Our results are consistent with spin-incoherent transport in a one-dimensional wire.
Silva, H; Muse, J; Lopes, M. C; Khakoo, M. A
doi: 10.1103/PhysRevLett.101.033201pmid: 18764253
Normalized differential cross sections for elastic (rotationally averaged) electron scattering from gaseous water ( H 2 O ) are obtained using the relative flow method against helium with a thin aperture collimating source of gas instead of a tube. This method obviates the use of gas kinetic molecular diameters for helium or water. Our measurements are found to be largely in quantitative disagreement with past differential elastic electron scattering measurements and suggest that present recommended electron scattering total cross sections for water be revised.
doi: 10.1103/PhysRevLett.101.037203pmid: 18764285
The magnetic properties of disordered graphene and irradiated graphite are systematically studied using a combination of mean-field Hubbard model and first-principles calculations. By considering large-scale disordered models of graphene, I conclude that only single-atom defects can induce ferromagnetism in graphene-based materials. The preserved stacking order of graphene layers is shown to be another necessary condition for achieving a finite net magnetic moment of irradiated graphite. Ab initio calculations of hydrogen binding and diffusion and of interstitial-vacancy recombination further confirm the crucial role of stacking order in π -electron ferromagnetism of proton-bombarded graphite.
doi: 10.1103/PhysRevLett.101.036101pmid: 18764266
The behavior of water under extreme confinement and, in particular, the lubrication properties under such conditions are subjects of long-standing controversy. Using a dedicated, high-resolution friction force microscope, scanning a sharp tungsten tip over a graphite surface, we demonstrate that water nucleating between the tip and the surface due to capillary condensation rapidly transforms into crystalline ice at room temperature. At ultralow scan speeds and modest relative humidities, we observe that the tip exhibits stick-slip motion with a period of 0.38 ± 0.03 nm , very different from the graphite lattice. We interpret this as the consequence of the repeated sequence of shear-induced fracture and healing of the crystalline condensate. This phenomenon causes a significant increase of the friction force and introduces relaxation time scales of seconds for the rearrangements after shearing.
Jia, Xun ; Goswami, Pallab ; Chakravarty, Sudip
doi: 10.1103/PhysRevLett.101.036805pmid: 18764276
The lowest Landau level of graphene is studied numerically by considering a tight-binding Hamiltonian with disorder. The Hall conductance σ x y and the longitudinal conductance σ x x are computed. We demonstrate that bond disorder can produce a plateaulike feature centered at ν = 0 , while the longitudinal conductance is nonzero in the same region, reflecting a band of extended states between ± E c , whose magnitude depends on the disorder strength. The critical exponent corresponding to the localization length at the edges of this band is found to be 2.47 ± 0.04 . When both bond disorder and a finite mass term exist the localization length exponent varies continuously between ∼ 1.0 and ∼ 7 / 3 .
doi: 10.1103/PhysRevLett.101.035002pmid: 18764259
Simple analytic formulas for energy relaxation (ER) in electron-ion systems, with quantum corrections, ion dynamics, and RPA-type screening are presented. ER in the presence of bound electrons is examined in view of recent simulations for ER in hydrogen in the range 10 20 – 10 24 electrons / cc .
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