17,078 research outputs found
Collective rearrangement at the onset of flow of a polycrystalline hexagonal columnar phase
Creep experiments on polycrystalline surfactant hexagonal columnar phases
show a power law regime, followed by a drastic fluidization before reaching a
final stationary flow. The scaling of the fluidization time with the shear
modulus of the sample and stress applied suggests that the onset of flow
involves a bulk reorganization of the material. This is confirmed by X-ray
scattering under stress coupled to \textit{in situ} rheology experiments, which
show a collective reorientation of all crystallites at the onset of flow. The
analogy with the fracture of heterogeneous materials is discussed.Comment: to appear in Phys. Rev. Let
Electronic Griffiths phase of the d=2 Mott transition
We investigate the effects of disorder within the T=0 Brinkman-Rice (BR)
scenario for the Mott metal-insulator transition (MIT) in two dimensions (2d).
For sufficiently weak disorder the transition retains the Mott character, as
signaled by the vanishing of the local quasiparticles (QP) weights Z_{i} and
strong disorder screening at criticality. In contrast to the behavior in high
dimensions, here the local spatial fluctuations of QP parameters are strongly
enhanced in the critical regime, with a distribution function P(Z) ~
Z^{\alpha-1} and \alpha tends to zero at the transition. This behavior
indicates a robust emergence of an electronic Griffiths phase preceding the
MIT, in a fashion surprisingly reminiscent of the "Infinite Randomness Fixed
Point" scenario for disordered quantum magnets.Comment: 4+ pages, 5 figures, final version to appear in Physical Review
Letter
Chiral spin-orbital liquids with nodal lines
Strongly correlated materials with strong spin-orbit coupling hold promise
for realizing topological phases with fractionalized excitations. Here we
propose a chiral spin-orbital liquid as a stable phase of a realistic model for
heavy-element double perovskites. This spin liquid state has Majorana fermion
excitations with a gapless spectrum characterized by nodal lines along the
edges of the Brillouin zone. We show that the nodal lines are topological
defects of a non-Abelian Berry connection and that the system exhibits
dispersing surface states. We discuss some experimental signatures of this
state and compare them with properties of the spin liquid candidate Ba_2YMoO_6.Comment: 5 pages + supplementary materia
Defect-induced spin-glass magnetism in incommensurate spin-gap magnets
We study magnetic order induced by non-magnetic impurities in quantum
paramagnets with incommensurate host spin correlations. In contrast to the
well-studied commensurate case where the defect-induced magnetism is spatially
disordered but non-frustrated, the present problem combines strong disorder
with frustration and, consequently, leads to spin-glass order. We discuss the
crossover from strong randomness in the dilute limit to more conventional glass
behavior at larger doping, and numerically characterize the robust short-range
order inherent to the spin-glass phase. We relate our findings to magnetic
order in both BiCu2PO6 and YBa2Cu3O6.6 induced by Zn substitution.Comment: 6 pages, 5 figs, (v2) real-space RG results added; discussion
extended, (v3) final version as publishe
On the -Dirac Oscillator revisited
This Letter is based on the -Dirac equation, derived from the
-Poincar\'{e}-Hopf algebra. It is shown that the -Dirac
equation preserves parity while breaks charge conjugation and time reversal
symmetries. Introducing the Dirac oscillator prescription,
, in the -Dirac
equation, one obtains the -Dirac oscillator. Using a decomposition in
terms of spin angular functions, one achieves the deformed radial equations,
with the associated deformed energy eigenvalues and eigenfunctions. The
deformation parameter breaks the infinite degeneracy of the Dirac oscillator.
In the case where , one recovers the energy eigenvalues and
eigenfunctions of the Dirac oscillator.Comment: 5 pages, no figures, accepted for publication in Physics Letters
Local roughness exponent in the nonlinear molecular-beam-epitaxy universality class in one-dimension
We report local roughness exponents, , for three
interface growth models in one dimension which are believed to belong the
non-linear molecular-beam-epitaxy (nMBE) universality class represented by the
Villain-Lais-Das Sarma (VLDS) stochastic equation. We applied an optimum
detrended fluctuation analysis (ODFA) [Luis et al., Phys. Rev. E 95, 042801
(2017)] and compared the outcomes with standard detrending methods. We observe
in all investigated models that ODFA outperforms the standard methods providing
exponents in the narrow interval consistent
with renormalization group predictions for the VLDS equation. In particular,
these exponent values are calculated for the Clarke-Vvdensky and Das
Sarma-Tamborenea models characterized by very strong corrections to the
scaling, for which large deviations of these values had been reported. Our
results strongly support the absence of anomalous scaling in the nMBE
universality class and the existence of corrections in the form
of the one-loop renormalization group analysis
of the VLDS equation
Memory effects on the statistics of fragmentation
We investigate through extensive molecular dynamics simulations the
fragmentation process of two-dimensional Lennard-Jones systems. After
thermalization, the fragmentation is initiated by a sudden increment to the
radial component of the particles' velocities. We study the effect of
temperature of the thermalized system as well as the influence of the impact
energy of the ``explosion'' event on the statistics of mass fragments. Our
results indicate that the cumulative distribution of fragments follows the
scaling ansatz , where is
the mass, and are cutoff parameters, and is a scaling
exponent that is dependent on the temperature. More precisely, we show clear
evidence that there is a characteristic scaling exponent for each
macroscopic phase of the thermalized system, i.e., that the non-universal
behavior of the fragmentation process is dictated by the state of the system
before it breaks down.Comment: 5 pages, 8 figure
- …