Experimental realization of a Rydberg optical Feshbach resonance in a quantum many-body system.

Feshbach resonances are a powerful tool to tune the interaction in an ultracold atomic gas. The commonly used magnetic Feshbach resonances are specific for each species and are restricted with respect to their temporal and spatial modulation. Optical Feshbach resonances are an alternative which can overcome this limitation.

The Effect of Dispersion on the Structure of Diphenyl Ether Aggregates.

Dispersion interactions can play an important role in understanding unusual binding behaviors. This is illustrated by a systematic study of the structural preferences of diphenyl ether (DPE)-alcohol aggregates, for which OH⋅⋅⋅O-bound or OH⋅⋅⋅π-bound isomers can be formed. The investigation was performed through a multi-spectroscopic approach including IR/UV and microwave methods, combined with a detailed theoretical analysis.

Continuous Easy-Plane Deconfined Phase Transition on the Kagome Lattice.

We use large scale quantum Monte Carlo simulations to study an extended Hubbard model of hard core bosons on the kagome lattice. In the limit of strong nearest-neighbor interactions at 1/3 filling, the interplay between frustration and quantum fluctuations leads to a valence bond solid ground state. The system undergoes a quantum phase transition to a superfluid phase as the interaction strength is decreased.

Emission Noise in an Interacting Quantum Dot: Role of Inelastic Scattering and Asymmetric Coupling to the Reservoirs.

A theory is developed for the emission noise at frequency ν in a quantum dot in the presence of Coulomb interactions and asymmetric couplings to the reservoirs. We give an analytical expression for the noise in terms of the various transmission amplitudes. Including the inelastic scattering contribution, it can be seen as the analog of the Meir-Wingreen formula for the current.

Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System.

We consider a hybrid quantum many-body system formed by a vibrational mode of a nanomembrane, which interacts optomechanically with light in a cavity, and an ultracold atom gas in the optical lattice of the out-coupled light. The adiabatic elimination of the light field yields an effective Hamiltonian which reveals a competition between the force localizing the atoms and the membrane displacement. At a critical atom-membrane interaction, we find a nonequilibrium quantum phase transition from a localized symmetric state of the atom cloud to a shifted symmetry-broken state, the energy of the lowest collective excitation vanishes, and a strong atom-membrane entanglement arises.

Optimized Spintronic Terahertz Emitters Based on Epitaxial Grown Fe/Pt Layer Structures.

We report on generation of pulsed broadband terahertz radiation utilizing the inverse spin hall effect in Fe/Pt bilayers on MgO and sapphire substrates. The emitter was optimized with respect to layer thickness, growth parameters, substrates and geometrical arrangement. The experimentally determined optimum layer thicknesses were in qualitative agreement with simulations of the spin current induced in the ferromagnetic layer.

Quantum Hamiltonian daemons: Unitary analogs of combustion engines.

Hamiltonian daemons have recently been defined classically as small, closed Hamiltonian systems which can exhibit secular energy transfer from high-frequency to low-frequency degrees of freedom (steady downconversion), analogous to the steady transfer of energy in a combustion engine from the high terahertz frequencies of molecular excitations to the low kilohertz frequencies of piston motion [L. Gilz, E. P.

Extreme event statistics in a drifting Markov chain.

We analyze extreme event statistics of experimentally realized Markov chains with various drifts. Our Markov chains are individual trajectories of a single atom diffusing in a one-dimensional periodic potential. Based on more than 500 individual atomic traces we verify the applicability of the Sparre Andersen theorem to our system despite the presence of a drift.

Perfect Spin Filter by Periodic Drive of a Ferromagnetic Quantum Barrier.

We consider the problem of particle tunneling through a periodically driven ferromagnetic quantum barrier connected to two leads. The barrier is modeled by an impurity site representing a ferromagnetic layer or a quantum dot in a tight-binding Hamiltonian with a local magnetic field and an ac-driven potential, which is solved using the Floquet formalism. The repulsive interactions in the quantum barrier are also taken into account.

Influence of Elastic Stiffness and Surface Adhesion on Bouncing of Nanoparticles.

Granular collisions are characterized by a threshold velocity, separating the low-velocity regime of grain sticking from the high-velocity regime of grain bouncing: the bouncing velocity, v . This parameter is particularly important for nanograins and has applications for instance in astrophysics where it enters the description of collisional dust aggregation. Analytic estimates are based on the macroscopic Johnson-Kendall-Roberts (JKR) theory, which predicts the dependence of v on the radius, elastic stiffness, and surface adhesion of grains.

Deuterated Molecular Ruby with Record Luminescence Quantum Yield.

The recently reported luminescent chromium(III) complex 1 ([Cr(ddpd) ] ; ddpd=N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (Φ=11 %) with a microsecond lifetime as the ligand design in 1 effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation.

Adhesion forces of the sea-water bacterium Paracoccus seriniphilus on titanium: Influence of microstructures and environmental conditions.

The bacterial attachment to surfaces is the first step of biofilm formation. This attachment is governed by adhesion forces which act between the bacterium and the substrate. Such forces can be measured by single cell force spectroscopy, where a single bacterium is attached to a cantilever of a scanning force microscope, and force-distance curves are measured.

The Structure of Diphenyl Ether-Methanol in the Electronically Excited and Ionic Ground States: A Combined IR/UV Spectroscopic and Theoretical Study.

Diphenyl ether offers competing docking sites for methanol: the ether oxygen acts as a common hydrogen-bond acceptor and the π system of each phenyl ring allows for OH-π interactions driven by electrostatic, induction, and dispersion forces. Based on investigations in the electronic ground state (S ), we present a detailed study of the electronically excited state (S ) and the ionic ground state (D ), in which an impact on the structural preference is expected compared with the S state. Dispersion forces in the electronically excited state were analyzed by comparing the computed binding energies at the coupled-cluster-singles (CCS) and approximate coupled-cluster-singles-doubles levels of theory (CC2 approximation).

Fully Atomistic Understanding of the Electronic and Optical Properties of a Prototypical Doped Charge-Transfer Interface.

The current study generates profound atomistic insights into doping-induced changes of the optical and electronic properties of the prototypical PTCDA/Ag(111) interface. For doping K atoms are used, as KPTCDA/Ag(111) has the distinct advantage of forming well-defined stoichiometric phases. To arrive at a conclusive, unambiguous, and fully atomistic understanding of the interface properties, we combine state-of-the-art density-functional theory calculations with optical differential reflectance data, photoelectron spectra, and X-ray standing wave measurements.

Electrostatic conditions define the 2D self-assembly of tomato bushy stunt viruses on solid surfaces.

Plant viruses which are self-assembled on a substrate are interesting building blocks in nanobiotechnology, in particular, for the creation of 2D ordered structures. In this article, the self-assembly of different genetically modified types of the tomato bushy stunt virus spin-coated on pristine silicon was investigated by scanning force and scanning electron microscopy. Amino acid side chains were integrated in the capsids of the viruses by extending the coat protein with different charged amino acid clusters (tetra-aspartate-hexa-histidine, hexa-aspartate, or tetra-arginine-tags).

Erratum: Padé resummation of many-body perturbation theories.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

A simple method to estimate the isoelectric point of modified Tomato bushy stunt virus (TBSV) particles.

We present a simple method to estimate the isoelectric point (pI) of Tomato Bushy Stunt particles. We demonstrate that the combination of agarose gels with different pH buffers can be used to electrophorese the virus particles and their migration patterns can be compared. This method allows us to estimate the pI of the virus particles (wild type, wt, and genetically modified particles) and to monitor the effect of the pI of modified peptide side chains of the viral capsid subunit on the pI of the whole virus particle.

Individual Tracer Atoms in an Ultracold Dilute Gas.

We report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the relaxation of the initial nonthermal state and detect the effect of single collisions which has so far eluded observation. We show that, after few collisions, the measured spatial distribution of the tracer atoms is correctly described by a Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers.

Multi-spectroscopic and theoretical analyses on the diphenyl ether-tert-butyl alcohol complex in the electronic ground and electronically excited state.

Aromatic ethers such as diphenyl ether (DPE) represent molecules with different docking sites for alcohols leading to competing OH-O and OH-π interactions. In a multi-spectroscopic approach in combination with quantum chemical calculations the complex of DPE with tert-butyl alcohol (t-BuOH) is investigated in the electronic ground state (S) and the electronically excited state (S). FTIR, microwave as well as mass- and isomer-selective IR/R2PI spectra are recorded, revealing co-existing OH-O and OH-π isomers in the S state.

Analyzing the influence of microstructured surfaces on the lactic acid production of in a flow-through cell system.

Microorganisms growing in biofilms might be possible biocatalysts for future biotechnological production processes. Attached to a surface and embedded in an extracellular polymeric matrix, they create their preferred environment and form robust cultures for continuous systems. With the objective of implementing highly efficient processes, productive biofilms need to be understood comprehensively.

Distinguishing attosecond electron-electron scattering and screening in transition metals.

Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening.

Measuring finite-range phase coherence in an optical lattice using Talbot interferometry.

One of the important goals of present research is to control and manipulate coherence in a broad variety of systems, such as semiconductor spintronics, biological photosynthetic systems, superconducting qubits and complex atomic networks. Over the past decades, interferometry of atoms and molecules has proven to be a powerful tool to explore coherence. Here we demonstrate a near-field interferometer based on the Talbot effect, which allows us to measure finite-range phase coherence of ultracold atoms in an optical lattice.

Removing biofilms from stainless steel without changing surface properties relevant for bacterial attachment.

The influence of oxygen (and argon) plasma cleaning and a base-acid cleaning procedure on stainless steel surfaces was studied. The main aim was to clean stainless steel samples from Paracoccus seriniphilus biofilms without changing the surface properties which are relevant for bacterial attachment to allow reuse in a biofilm reactor. It is shown that oxygen plasma cleaning, which very successfully removes the same kind of biofilm from titanium surfaces, is not suitable for stainless steel.