Physical Review Letters

Ruffoni, M. P; Pascarelli, S. P

doi: 10.1103/PhysRevLett.101.147202pmid: 18851565

Using differential x-ray absorption spectroscopy (DiffXAS) we have measured and quantified the intrinsic, atomic-scale magnetostriction of Fe 81 Ga 19 . By exploiting the chemical selectivity of DiffXAS, the Fe and Ga local environments have been assessed individually. The enhanced magnetostriction induced by the addition of Ga to Fe was found to originate from the Ga environment, where <?format ?> λ γ , 2 ( ≈ ( 3 / 2 ) λ 100 ) is 390 ± 40 ppm . In this environment, ⟨ 001 ⟩ Ga-Ga pair defects were found to exist, which mediate the magnetostriction by inducing large strains in the surrounding Ga-Fe bonds. For the first time, intrinsic, chemically selective magnetostrictive strain has been measured and quantified at the atomic level, allowing true comparison with theory.

Kankainen, A; Elomaa, V.-V; Batist, L; Eliseev, S; Eronen, T; Hager, U; Hakala, J; Jokinen, A; Moore, I. D; Novikov, Yu. N; Penttilä, H. N; Popov, A. N; Rahaman, S. N; Rinta-Antila, S. N; Rissanen, J. N; Saastamoinen, A. N;

Trebst, Simon ; Ardonne, Eddy ; Feiguin, Adrian ; Huse, David A; Ludwig, Andreas W; Troyer, Matthias W

doi: 10.1103/PhysRevLett.101.149901pmid: N/A

Wiseman, Howard M; Gambetta, J. M

doi: 10.1103/PhysRevLett.101.140401pmid: 18851507

Since the first derivation of non-Markovian stochastic Schrödinger equations, their interpretation has been contentious. In a recent Letter Phys. Rev. Lett. 100 , 080401 ( 2008 ) PRLTAO 0031-9007 10.1103/PhysRevLett.100.080401 , Diósi claimed to prove that they generate “true single system trajectories conditioned on continuous measurement.” In this Letter, we show that his proof is fundamentally flawed: the solution to his non-Markovian stochastic Schrödinger equation at any particular time can be interpreted as a conditioned state, but joining up these solutions as a trajectory creates a fiction.

Ruff, J. P; Clancy, J. P; Bourque, A. P; White, M. A; Ramazanoglu, M. A; Gardner, J. S; Qiu, Y. S; Copley, J. R; Johnson, M. B; Dabkowska, H. A; Gaulin, B. D

doi: 10.1103/PhysRevLett.101.147205pmid:

Jörg, Thomas ; Krzakala, Florent ; Kurchan, Jorge ; Maggs, A. C

doi: 10.1103/PhysRevLett.101.147204pmid: 18851567

We study first-order quantum phase transitions in mean-field spin glasses. We solve the quantum random energy model using elementary methods and show that at the transition the eigenstate suddenly projects onto the unperturbed ground state and that the gap between the lowest states is exponentially small in the system size. We argue that this is a generic feature of all “random first-order” models, which includes benchmarks such as random satisfiability. We introduce a two-time instanton to calculate this gap in general, and discuss the consequences for quantum annealing.

Schirotzek, André ; Shin, Yong-il ; Schunck, Christian H; Ketterle, Wolfgang H

doi: 10.1103/PhysRevLett.101.140403pmid: 18851509

We present majority and minority radio frequency spectra of strongly interacting imbalanced Fermi gases of Li 6 . We observed a smooth evolution in the nature of pairing correlations from pairing in the superfluid region to polaron binding in the highly polarized normal region. The imbalance induces quasiparticles in the superfluid region even at very low temperature. This leads to a local bimodal spectral response, which allowed us to determine the superfluid gap Δ and the Hartree energy U .

Tripathi, Vandana ; Tabor, S. L; Mantica, P. F; Utsuno, Y. F; Bender, P. F; Cook, J. F; Hoffman, C. R; Lee, Sangjin R; Otsuka, T. R; Pereira, J. R; Perry, M. R; Pepper, K. R; Pinter, J. S; Stoker, J. S; Volya, A. S; Weisshaar, D. S

Helander, P; Simakov, A. N

doi: 10.1103/PhysRevLett.101.145003pmid: 18851538

It is shown that collisional plasma transport is intrinsically ambipolar only in quasiaxisymmetric or quasihelically symmetric magnetic configurations. Only in such fields can the plasma rotate freely, and then only in the direction of quasisymmetry. In a non-quasi-symmetric magnetic field, the average radial electric field is determined by parallel viscosity, which in turn is usually governed by collisional processes. Locally, the radial electric field may be affected by turbulent Reynolds stress producing zonal flows, but on a radial average taken over several ion gyroradii, it is determined by parallel viscosity, at least if the turbulence is electrostatic and obeys the conventional gyrokinetic orderings. This differs from the situation in a tokamak, where there is no flow damping by parallel viscosity in the symmetry direction and the turbulent Reynolds stress may affect the global radial electric field.

Levitas, Valery I; Altukhova, Nataliya I

doi: 10.1103/PhysRevLett.101.145703pmid: 18851543

Thermodynamic and kinetic approaches for sublimation inside elastoplastic material under tensile stress are developed for large strains. Various conceptual problems related to irreversible plastic deformation are addressed for a spherical bubble. They include definitions of the thermodynamic driving forces and activation energies, nontraditional concepts of a critical nucleus, path dependence of its appearance, modes of its growth (sublimation or expansion due to loss of mechanical stability), and the possibility of reverse transformation. The kinetic relationships between sublimation pressure and temperature are obtained.