Complex photoconductive measurements of the current through a double quantum dot enable us to monitor effects of coherent electron transport in the suppression of the rabi oscillations of this “artificial molecule.” The current is induced by a new broadband millimeter wave source functioning as a heterodyne interferometer, which consists of two nonlinear transmission lines generating harmonic outputs in the range 2–400 GHz, and, being coherent, allows tracking the induced current through the sample in both magnitude and phase.

We have studied the temporal coherence of high-order harmonics (up to the 15th order) produced by focusing 100 fs laser pulses into an argon gas jet. We measure the visibility of the interference fringes, produced when two spatially separated harmonic sources interfere in the far field, as a function of the time delay between the two sources. In general, we find long coherence times, comparable to the expected pulse durations of the harmonics. For some of the harmonics, the interference pattern exhibits two regions, with significantly different coherence times. These results are interpreted in terms of different electronic trajectories contributing to harmonic generation.

The top layer of the $\mathrm{GaAs}\left(001\right)-(2\times 4)$ surface consists of rows of As-As dimers. However, our scanning tunneling microscopy study shows that, in the initial adsorption stage, monoenergetic ${\mathrm{Br}}_2$ molecules (0.89 eV) react exclusively with the second layer Ga atoms exposed in trenches or at defects on the surface. A simple molecular orbital argument was used to explain the dynamics of forming gallium bromide species at various surface Ga sites.

We describe a new instability mechanism in free dendrite growth, which arises from electrically enhanced diffusion of polar molecules near the dendrite tip. For a small applied potential, the dendrite tip velocity increases slowly with potential, as is described by an extension of normal solvability theory. Above a threshold potential, however, capillarity is insufficient to stabilize growth. We present observations that confirm this instability, which brings about a transition from enhanced normal dendrite growth to a rapidly growing needle morphology with strongly suppressed sidebranching.

Using the Landauer formulation of transport theory, we predict that dielectric quantum wires should exhibit quantized thermal conductance at low temperatures in a ballistic phonon regime. The quantum of thermal conductance is universal, independent of the characteristics of the material, and equal to ${\pi }^2{k}_B^{2}T/3h$ where $k_B$ is the Boltzmann constant, $h$ is Planck's constant, and $T$ is the temperature. Quantized thermal conductance should be experimentally observable in suspended nanostructures adiabatically coupled to reservoirs, devices that can be realized at the present time.

Definitive evidence from a plasma wave interferometer carried on a sounding rocket is presented for the observation of counterrotating electric field structures observed at frequencies above and below the local lower hybrid resonance frequency, $f_{\mathrm{LHR}}$, of the ambient plasma. These counterrotating structures were observed within the context of a lower hybrid solitary structure (LHSS), and were found to rotate in a right-handed (left-handed) sense around the geomagnetic field at frequencies above (below) $f_{\mathrm{LHR}}$, in accord with previous predictions for and observations of electric field eigenmodes within a density depletion. The presence of a narrow band feature below $f_{\mathrm{LHR}}$ indicates the presence of trapped waves, and represents clear evidence of a bound state of lower hybrid waves in the auroral ionosphere.

We have completely determined the amplitude and phase of a quantum wave packet. The wave packet was shaped using a programmable optical pulse. Phase information comes from analysis of covariant fluctuations due to interference between the wave packet and a well-characterized reference.

In this Letter we present an experimental analysis of the acoustic transmission of a two-dimensional periodic array of rigid cylinders in air with two different geometrical configurations: square and triangular. In both configurations, and above a certain filling fraction, we observe an overlap, in the range of the audible frequencies, between the attenuation peaks measured along the two high-symmetry directions of the Brillouin zone. This effect is considered as the fingerprint of the existence of a full acoustic gap. Nevertheless, the comparison with our calculation of band structures shows that the triangular lattice has band states in that frequency range. We call them deaf bands. This contradictory result is explained by looking at the symmetry of the deaf bands; they cannot be excited by experiments of sound transmission.

Atomic force microscopy on hydrophobic microspheres in water reveals a strong attraction with a range of 20–200 nm, following an initial steep repulsion at long range. The data are consistent with a single submicroscopic bubble between the surfaces, with the attraction due to its attachment and lateral spread, and the repulsion dependent on film drainage and the electric double layer. The results provide direct experimental evidence of the existence of long-lived submicron bubbles, and of their bridging as the cause of the measured long-range attractions between macroscopic hydrophobic surfaces.

We show that stationary wave solutions of reaction-diffusion equations obey Snell's law of refraction. Refraction occurs at the interface of media where local kinetics have different reaction rates and the same steady state. In particular, we show that the apparent reflection or back refraction observed in experiments is also derived from Snell's law.

We show that gravitational radiation drives an instability in hot young rapidly rotating neutron stars. This instability occurs primarily in the $l=2\mathrm{}$ $r$-mode and will carry away most of the angular momentum of a rapidly rotating star by gravitational radiation. On the time scale needed to cool a young neutron star to about ${T=10\mathrm{}}^9\mathrm{K}$ (about one year) this instability can reduce the rotation rate of a rapidly rotating star to about $0.076{\Omega }_K$, where ${\Omega }_K$ is the Keplerian angular velocity where mass shedding occurs. In older colder neutron stars this instability is suppressed by viscous effects, allowing older stars to be spun up by accretion to larger angular velocities.

We demonstrate that the well-known $\mathrm{Si}\left(111\right)-(7\times 7)$ superlattice buried under as much as 100 Å of crystalline Pb can be directly imaged with a scanning tunneling microscope at 77 K. The unexpected transparency of the metal and the high lateral resolution are the result of a nondiffractive scattering of the electrons at the interface. We attribute this phenomenon to a large anisotropy of the effective masses associated with the free in-plane and the quantized transverse motion of the electrons.

It is experimentally demonstrated that a transition from a synclinic to an anticlinic liquid crystal phase occurs via stable domain wall propagation after quenching in a uniform temperature field. Such a one-dimensional growth may be explained in terms of a nonlinear diffusion equation. The experiment provides the first example of free, one-dimensional growth in a system subjected to a pure and uniform temperature field.

We report the first real time imaging of single fluorophores attached to protein molecules on metal surfaces in aqueous solution using surface plasmon resonance fluorescence microscopy. The fluorescence was enhanced by the surface plasmons as theoretically predicted for gold and silver. Active movement of single molecules of the fluorescently labeled motor protein, coupled to the ATPase reaction, was observed on the surfaces of gold and aluminum. This microscopy should prove a powerful tool to directly detect single molecule processes in biomolecule systems organized on a metal surface.

We report on the experimental observation of environment induced decoherence in the quantum delta-kicked rotor. Ultracold cesium atoms are subjected to a pulsed standing wave of near resonant light. Spontaneous scattering of photons destroys dynamical localization thereby giving rise to a quantum diffusion, which approaches the classical diffusion with an increasing degree of decoherence. This tendency is enhanced by a stronger stochasticity in the underlying classical system. A comparison with theoretical predictions is presented.

The combination of cold atoms and large coherent coupling enables investigations in a new regime in cavity QED with single-atom trajectories monitored in real time with high signal-to-noise ratio. The underlying “vacuum-Rabi” splitting is clearly reflected in the frequency dependence of atomic transit signals recorded atom by atom, with evidence for mechanical light forces for intracavity photon number $<1\mathrm{}$. The nonlinear optical response of one atom in a cavity is observed to be in accord with the one-atom quantum theory but at variance with semiclassical predictions.

We experimentally entangle freely propagating particles that never physically interacted with one another or which have never been dynamically coupled by any other means. This demonstrates that quantum entanglement requires the entangled particles neither to come from a common source nor to have interacted in the past. In our experiment we take two pairs of polarization entangled photons and subject one photon from each pair to a Bell-state measurement. This results in projecting the other two outgoing photons into an entangled state.

Breakup temperatures in central collisions of ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$ at bombarding energies $E/A=50\mathrm{}$ to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 to 12 MeV, in qualitative agreement with a scenario of chemical freeze-out after adiabatic expansion. Excited-state temperatures, derived from yield ratios of states in ${}^4\mathrm{He}$, ${}^{5,6}\mathrm{Li}$, and ${}^8\mathrm{Be}$, are about 5 MeV, independent of the projectile energy, and seem to reflect the internal temperature of fragments at their final separation from the system.

We report a principle that allows one to write visible light emitting silicon patterns of arbitrary shape down to the submicrometer scale. We demonstrate that porous Si growth can electrochemically be initiated preferentially at surface defects created in an $n$-type Si substrate by ${\mathrm{Si}}^{++}$ focused ion beam bombardment. For $n$-type material in the dark, the electrochemical pore formation potential (Schottky barrier breakdown voltage) is significantly lower at the implanted locations than for an unimplanted surface. This difference in the threshold voltages is exploited to achieve the selectivity of the pore formation process.

We study the equilibrium phase diagram of binary mixtures of hard spheres as well as of parallel hard cubes. A superior cluster algorithm allows us to establish and to access the demixed phase for both systems and to investigate the subtle interplay between short-range depletion and long-range demixing.