Topical Issue on many particle spectroscopy of atoms, molecules, clusters and surfaces editorial: Editorial.

Many particle spectroscopy is a subject of continued interest to many experimental and theoretical groups worldwide. It is based on the coincidence spectroscopy of minimum two particles coming from the same elementary process. It is a very powerful tool for studying not just atoms and molecules but also more extended electronic systems such as clusters and surfaces.

Sub-lattice of Jahn-Teller centers in hexaferrite crystal.

A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFeO. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect.

Nanosecond Spin Coherence Time of Nonradiative Excitons in GaAs/AlGaAs Quantum Wells.

We report on the experimental evidence for a nanosecond timescale spin memory based on nonradiative excitons with large in-plane wave vector. The effect manifests itself in magnetic-field-induced oscillations of the energy of the optically active (radiative) excitons. The oscillations detected by a spectrally resolved pump-probe technique applied to a GaAs/AlGaAs quantum well structure in a transverse magnetic field persist over a timescale, which is orders of magnitude longer than the characteristic decoherence time in the system.

Tracking Dark Excitons with Exciton Polaritons in Semiconductor Microcavities.

Dark excitons are of fundamental importance for a wide variety of processes in semiconductors but are difficult to investigate using optical techniques due to their weak interaction with light fields. We reveal and characterize dark excitons nonresonantly injected into a semiconductor microcavity structure containing InGaAs/GaAs quantum wells by a gated train of eight 100 fs pulses separated by 13 ns by monitoring their interactions with the bright lower polariton mode. We find a surprisingly long dark exciton lifetime of more than 20 ns, which is longer than the time delay between two consecutive pulses.

Very weak oscillating magnetic field disrupts the magnetic compass of songbird migrants.

Previously, it has been shown that long-distance migrants, garden warblers (), were disoriented in the presence of narrow-band oscillating magnetic field (1.403 MHz OMF, 190 nT) during autumn migration. This agrees with the data of previous experiments with European robins ().

Low-Frequency Dynamics of BSA Complementarily Studied by Raman and Inelastic Neutron Spectroscopy.

The present study focuses on protein motions on the picosecond time scale, generally characterized by the overlapping of vibrational and relaxational dynamics in disordered molecular systems. Recently, it has been demonstrated that a dry protein, bovine serum albumin (BSA), shows a glass-like transition in the temperature range between 240 and 260 K. Here, we present the results of combined low-frequency Raman and inelastic neutron scattering studies of dry BSA under conditions similar to those of this glass-like transition.

Study of the phase transition in lysozyme crystals by Raman spectroscopy.

Background: Recently, it has been revealed that tetragonal lysozyme crystals show a phase transition at 307 K upon heating. The underlying mechanisms of the phase transition are still not fully understood. Here we focus on the study of high-frequency vibrational modes arising from the protein and their temperature evolution in the vicinity of Tph as well as on the detailed study of crystalline water dynamics near Tph.

Photon-Statistics Excitation Spectroscopy of a Quantum-Dot Micropillar Laser.

We introduce photon-statistics excitation spectroscopy and exemplarily apply it to a quantum-dot micropillar laser. Both the intensity and the photon number statistics of the emission from the micropillar show a strong dependence on the photon statistics of the light used for excitation of the sample. The results under coherent and pseudothermal excitation reveal that a description of the laser properties in terms of mean input photon numbers is not sufficient.

Helicity-Driven Ratchet Effect Enhanced by Plasmons.

We demonstrate that the ratchet effect-a radiation-induced direct current in periodically modulated structures with built-in asymmetry-is dramatically enhanced in the vicinity of the plasmonic resonances and has a nontrivial polarization dependence. For a circular polarization, the current component, perpendicular to the modulation direction, changes sign with the inversion of the radiation helicity. In the high-mobility structures, this component might increase by several orders of magnitude due to the plasmonic effects and exceed the current component in the modulation direction.

Revealing the mechanism of the low-energy electron yield enhancement from sensitizing nanoparticles.

We provide a physical explanation for the enhancement of the low-energy electron production by sensitizing nanoparticles due to irradiation by fast ions. It is demonstrated that a significant increase in the number of emitted electrons arises from the collective electron excitations in the nanoparticle. We predict a new mechanism of the yield enhancement due to the plasmon excitations and quantitatively estimate its contribution to the electron production.

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions.

Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified.

Lasing from active optomechanical resonators.

Planar microcavities with distributed Bragg reflectors (DBRs) host, besides confined optical modes, also mechanical resonances due to stop bands in the phonon dispersion relation of the DBRs. These resonances have frequencies in the 10- to 100-GHz range, depending on the resonator's optical wavelength, with quality factors exceeding 1,000. The interaction of photons and phonons in such optomechanical systems can be drastically enhanced, opening a new route towards the manipulation of light.

Magnetic orientation of garden warblers (Sylvia borin) under 1.4 MHz radiofrequency magnetic field.

We report on the experiments on orientation of a migratory songbird, the garden warbler (Sylvia borin), during the autumn migration period on the Courish Spit, Eastern Baltics. Birds in experimental cages, deprived of visual information, showed the seasonally appropriate direction of intended flight with respect to the magnetic meridian. Weak radiofrequency (RF) magnetic field (190 nT at 1.

Firing clamp: a novel method for single-trial estimation of excitatory and inhibitory synaptic neuronal conductances.

Understanding non-stationary neuronal activity as seen in vivo requires estimation of both excitatory and inhibitory synaptic conductances from a single trial of recording. For this purpose, we propose a new intracellular recording method, called "firing clamp." Synaptic conductances are estimated from the characteristics of artificially evoked probe spikes, namely the spike amplitude and the mean subthreshold potential, which are sensitive to both excitatory and inhibitory synaptic input signals.

Coherent coupling of excitons and trions in a photoexcited CdTe/CdMgTe quantum well.

We present zero-, one-, and two-quantum two-dimensional coherent spectra of excitons and trions in a CdTe/(Cd,Mg)Te quantum well. The set of spectra provides a unique and comprehensive picture of the coherent nonlinear optical response. Distinct peaks in the spectra are manifestations of exciton-exciton and exciton-trion coherent coupling.

Does a dry protein undergo a glass transition?

Bovine serum albumin (BSA) with extremely low hydration level 0.04, which is usually defined as dry, has been investigated in the temperature range between 200 and 340 K by incoherent inelastic neutron scattering using the neutron time-of-flight spectrometer FOCUS (PSI, Switzerland). Anomalous temperature behavior has been revealed for relaxational and low-frequency vibrational dynamics of BSA in the vicinity of 250 K.

A simple Markov model of sodium channels with a dynamic threshold.

Characteristics of action potential generation are important to understanding brain functioning and, thus, must be understood and modeled. It is still an open question what model can describe concurrently the phenomena of sharp spike shape, the spike threshold variability, and the divisive effect of shunting on the gain of frequency-current dependence. We reproduced these three effects experimentally by patch-clamp recordings in cortical slices, but we failed to simulate them by any of 11 known neuron models, including one- and multi-compartment, with Hodgkin-Huxley and Markov equation-based sodium channel approximations, and those taking into account sodium channel subtype heterogeneity.

Origin of easy magnetization switching in magnetic tunnel junctions with voltage-controlled interfacial anisotropy.

Spin-polarized currents represent an efficient tool for manipulating ferromagnetic nanostructures but the critical current density necessary for the magnetization switching is usually too high for applications. Here we show theoretically that, in magnetic tunnel junctions having electric-field-dependent interfacial anisotropy, the critical density may reduce down to a very low level (~10(4) A cm(-2)) when the junction combines small conductance with the proximity of free layer to a size-driven spin reorientation transition. The theory explains easy magnetization switching recently discovered in CoFeB/MgO/CoFeB tunnel junctions, surprisingly showing that it happens when the spin-transfer torque is relatively small, and provides a recipe for the fabrication of magnetic tunnel junctions suitable for industrial memory applications.

Conductance-based refractory density model of primary visual cortex.

A layered continual population model of primary visual cortex has been constructed, which reproduces a set of experimental data, including postsynaptic responses of single neurons on extracellular electric stimulation and spatially distributed activity patterns in response to visual stimulation. In the model, synaptically interacting excitatory and inhibitory neuronal populations are described by a conductance-based refractory density approach. Populations of two-compartment excitatory and inhibitory neurons in cortical layers 2/3 and 4 are distributed in the 2-d cortical space and connected by AMPA, NMDA and GABA type synapses.

Common features of low-temperature spin-charge separation and superlattice formation in multiferroic manganites and antiferromagnetic cuprates.

The paper reports on new results obtained for tetragonal quasi-2D antiferromagnetic Eu2CuO4 at temperatures below 30-40 K. A set of ferromagnetic resonance lines similar to ones obtained earlier for a number of multiferroic manganites (Sanina et al 2012 J. Phys.

Spin-wave excitations in superlattices self-assembled in multiferroic single crystals.

Spin-wave excitations revealed in the dynamically equilibrated one-dimensional superlattices formed due to phase separation and charge carrier self-organization in doped single crystals of Eu(0.8)Ce(0.2)Mn(2)O(5) and Tb(0.

Dynamic spin polarization by orientation-dependent separation in a ferromagnet-semiconductor hybrid.

Integration of magnetism into semiconductor electronics would facilitate an all-in-one-chip computer. Ferromagnet/bulk semiconductor hybrids have been, so far, mainly considered as key devices to read out the ferromagnetism by means of spin injection. Here we demonstrate that a Mn-based ferromagnetic layer acts as an orientation-dependent separator for carrier spins confined in a semiconductor quantum well that is set apart from the ferromagnet by a barrier only a few nanometers thick.

Magnetic properties of multiferroics-semiconductors Eu(1-x)Ce(x)Mn2O5.

Studies of magnetization, magnetoresistance, and magnetic oscillations in semiconductor-multiferroics Eu(1-x)Ce(x)Mn2O5 (x = 0.2-0.25) (ECMO) at temperatures ranging from 5 to 350 K in magnetic fields up to 6 T are presented.

Observation of interface carrier states in no-common-atom heterostructures ZnSe/BeTe.

The existence of intrinsic carrier interface states in heterostructures with no common atom at the interface (such as ZnSe/BeTe) is shown experimentally by ellipsometry and photoluminescence spectroscopy. These states are located on interfaces and lie inside the effective bandgap of the structure; they are characterized by a high density and a long lifetime. A tight binding model confirms theoretically the existence of these states in ZnSe/BeTe heterostructures for a ZnTe-type interface, in contrast to the case of the BeSe-type interface for which they do not exist.