Hot Brownian Motion

We derive the generalized Markovian description for the non-equilibrium Brownian motion of a heated particle in a simple solvent with a temperature-dependent viscosity. Our analytical results for the generalized fluctuation-dissipation and Stokes-Einstein relations compare favorably with measurements of laser-heated gold nano-particles and provide a practical rational basis for emerging photothermal technologies.Comment: 10 pages, 5 figure

Jamming, two-fluid behaviour and 'self-filtration' in concentrated particulate suspensions

We study the flow of model experimental hard sphere colloidal suspensions at high volume fraction $\Phi$ driven through a constriction by a pressure gradient. Above a particle-size dependent limit $\Phi_0$, direct microscopic observations demonstrate jamming and unjamming--conversion of fluid to solid and vice versa--during flow. We show that such a jamming flow produces a reduction in colloid concentration $\Phi_{x}$ downstream of the constriction. We propose that this `self-filtration' effect is the consequence of a combination of jamming of the particulate part of the system and continuing flow of the liquid part, i.e. the solvent, through the pores of the jammed solid. Thus we link the concept of jamming in colloidal and granular media with a 'two-fluid'-like picture of the flow of concentrated suspensions. Results are also discussed in the light of Osborne Reynolds' original experiments on dilation in granular materials.Comment: 4 pages, 3 figure

BiFeO3/La0.7Sr0.3MnO3 heterostructures deposited on Spark Plasma Sintered LaAlO3 Substrates

Multiferroic BiFeO3 (BFO) / La0.7Sr0.3MnO3 heterostructured thin films were grown by pulsed laser deposition on polished spark plasma sintered LaAlO3 (LAO) polycrystalline substrates. Both polycrystalline LAO substrates and BFO films were locally characterized using electron backscattering diffraction (EBSD), which confirmed the high-quality local epitaxial growth on each substrate grain. Piezoforce microscopy was used to image and switch the piezo-domains, and the results are consistent with the relative orientation of the ferroelectric variants with the surface normal. This high-throughput synthesis process opens the routes towards wide survey of electronic properties as a function of crystalline orientation in complex oxide thin film synthesis.Comment: 10 pages, 4 figures, Submitted to Applied Physics Letter

Overarching framework between Gaussian quantum discord and Gaussian quantum illumination

We cast the problem of illuminating an object in a noisy environment into a communication protocol. A probe is sent into the environment, and the presence or absence of the object constitutes a signal encoded on the probe. The probe is then measured to decode the signal. We calculate the Holevo information and bounds to the accessible information between the encoded and received signal with two different Gaussian probes---an Einstein-Podolsky-Rosen (EPR) state and a coherent state. We also evaluate the Gaussian discord consumed during the encoding process with the EPR probe. We find that the Holevo quantum advantage, defined as the difference between the Holevo information obtained from the EPR and coherent state probes, is approximately equal to the discord consumed. These quantities become exact in the typical illumination regime of low object reflectivity and low probe energy. Hence we show that discord is the resource responsible for the quantum advantage in Gaussian quantum illumination.Comment: 12 pages, 8 figure

Correlation length by measuring empty space in simulated aggregates

We examine the geometry of the spaces between particles in diffusion-limited cluster aggregation, a numerical model of aggregating suspensions. Computing the distribution of distances from each point to the nearest particle, we show that it has a scaled form independent of the concentration phi, for both two- (2D) and three-dimensional (3D) model gels at low phi. The mean remoteness is proportional to the density-density correlation length of the gel, xi, allowing a more precise measurement of xi than by other methods. A simple analytical form for the scaled remoteness distribution is developed, highlighting the geometrical information content of the data. We show that the second moment of the distribution gives a useful estimate of the permeability of porous media.Comment: 4 page

Does gravity cause load-bearing bridges in colloidal and granular systems?

We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings

Laboratory measurement of large‐amplitude whistler pulses generated by fast magnetic reconnection

We present observations of large‐amplitude (δB/B∼ 0.01) oblique whistler wave pulses generated by a spontaneous, 3‐D localized magnetic reconnection event in the Caltech jet experiment. The wave pulses are measured more than 50 ion skin depths from the reconnection location by a tetrahedron array of three‐axis B‐dot probes that mimic the pyramid flight formations of the Cluster and Magnetospheric Multiscale Mission spacecraft. Measurements of background parameters, wave polarization, and wave dispersion confirm that the pulses are whistler modes. These results demonstrate that localized impulsive reconnection events can generate large‐amplitude, oblique whistler wave pulses that propagate far outside the reconnection region. This provides a new pathway for the generation of magnetospheric whistler pulses and may help explain relativistic particle acceleration in phenomena such as solar flares that incorporate 3‐D localized impulsive magnetic reconnection