Unusual behaviour of the spin-phonon coupling in the quasi-one-dimensional antiferromagnet RbCoCl.

We present an experimental and theoretical study for the lattice vibrational (phonon) modes in the quasi-one-dimensional (or chain-like) antiferromagnet RbCoCl at low temperatures both above and below the two different magnetic phase transitions. Clear evidence is found for the role of spin-phonon interactions in providing a temperature-dependent contribution for the frequencies of the E and E symmetry phonons that occur with frequencies comparable to those of the spin wave excitations (magnons) in this compound. The behaviour in RbCoCl, as studied here by Raman scattering experiments, is quite different from that typically observed in rutile-structure antiferromagnets where the spin-phonon coupling has been well characterized.

Genomic signatures of Lake Erie bacteria suggest interaction in the Microcystis phycosphere.

Microbial interactions in harmful algal bloom (HAB) communities have been examined in marine systems, but are poorly studied in fresh waters. To investigate HAB-microbe interactions, we isolated bacteria with close associations to bloom-forming cyanobacteria, Microcystis spp., during a 2017 bloom in the western basin of Lake Erie.

Genomics of Environmental : Engaging Students in the Microbiology and Bioinformatics of Foodborne Pathogens.

We have developed and implemented an undergraduate microbiology course in which students isolate, characterize, and perform whole genome assembly and analysis of from stream sediments and poultry litter. In the development of the course and over three semesters, successive teams of undergraduate students collected field samples and performed enrichment and isolation techniques specific for the detection of . Eighty-eight strains were confirmed using standard microbiological methods and PCR of the gene.

Formation of colloidal alloy semiconductor CdTeSe magic-size clusters at room temperature.

Alloy semiconductor magic-size clusters (MSCs) have received scant attention and little is known about their formation pathway. Here, we report the synthesis of alloy CdTeSe MSC-399 (exhibiting sharp absorption peaking at 399 nm) at room temperature, together with an explanation of its formation pathway. The evolution of MSC-399 at room temperature is detected when two prenucleation-stage samples of binary CdTe and CdSe are mixed, which are transparent in optical absorption.

Bright photoluminescence from ordered arrays of SiGe nanowires grown on Si(111).

We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.

Nickel hydroxides and related materials: a review of their structures, synthesis and properties.

This review article summarizes the last few decades of research on nickel hydroxide, an important material in physics and chemistry, that has many applications in engineering including, significantly, batteries. First, the structures of the two known polymorphs, denoted as -Ni(OH) and -Ni(OH), are described. The various types of disorder, which are frequently present in nickel hydroxide materials, are discussed including hydration, stacking fault disorder, mechanical stresses and the incorporation of ionic impurities.

Selective growth and ordering of SiGe nanowires for band gap engineering.

Selective growth and self-organization of silicon-germanium (SiGe) nanowires (NWs) on focused ion beam (FIB) patterned Si(111) substrates is reported. In its first step, the process involves the selective synthesis of Au catalysts in SiO₂-free areas; its second step involves the preferential nucleation and growth of SiGe NWs on the catalysts. The selective synthesis process is based on a simple, room-temperature reduction of gold salts (Au³⁺Cl₄⁻) in aqueous solution, which provides well-organized Au catalysts.

Applications of in situ Raman spectroscopy for identifying nickel hydroxide materials and surface layers during chemical aging.

The applications of in situ vibrational spectroscopy for identifying bulk and surface Ni(OH)2 are discussed. Raman spectra from α- and β-Ni(OH)2 samples immersed in water are generally similar to those collected from comparable dry samples. However, the Raman scattering intensities vary, and dry β-Ni(OH)2 additionally exhibits a surface O-H stretching mode at 3690 cm(-1).

Raman and infrared spectroscopy of α and β phases of thin nickel hydroxide films electrochemically formed on nickel.

The present work utilizes Raman and infrared (IR) spectroscopy, supported by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to re-examine the fine structural details of Ni(OH)(2), which is a key material in many energy-related applications. This work also unifies the large body of literature on the topic. Samples were prepared by the galvanostatic basification of nickel salts and by aging the deposits in hot KOH solutions.

Photoluminescence efficiency and size distribution of self assembled ge dots on porous TiO2.

For Ge nanodots approximately 20 nm in diameter grown by annealing a thin amorphous Ge layer deposited by molecular beam epitaxy on a mesoporous TiO2 layer on Si(001), photoluminescence (PL) was observed as a wide near-infrared band near 800 meV. Using a tight binding theoretical model, the energy-dependent PL spectrum was transformed into a dependence on dot size. The average dot size determined the peak energy of the PL band and its shape depended on the size distribution, including bandgap enlargement due to quantum confinement.

Direct observation of polarons in electron populated quantum dots by resonant Raman scattering.

The general problem of the pairing of strongly interacting elementary excitations producing new quasiparticles such as polarons arises in many areas of solid state physics. Recent interest in polaron formation in semiconductor quantum dots has been motivated by the need to understand the physical nature of the carrier relaxation processes and their role in quantum-dot based devices. We report on the direct observation of polarons in InAs/GaAs self-assembled quantum dots populated by few electrons where the polarons are strongly coupled modes of quantum dot phonons and electron intersublevel transitions.

Spin waves in nickel nanorings of large aspect ratio.

The spin dynamics of high-aspect-ratio nickel nanorings in a longitudinal magnetic field have been investigated by Brillouin spectroscopy and the results are compared with a macroscopic theory and three-dimensional micromagnetic simulations. Good agreement is found between the measured and calculated magnetic field dependence of the spin wave frequency. Simulations show that as the field decreases from saturation, the rings switch from a "bamboo" to a novel "twisted bamboo" state at a certain critical field, and predict a corresponding dip in the dependence of the spin wave frequency on the magnetic field.

Magnon squeezing in an antiferromagnet: reducing the spin noise below the standard quantum limit.

We report the first experimental demonstration of quantum squeezing of a collective spin-wave excitation (magnon) using femtosecond optical pulses to generate correlations involving pairs of spins in an antiferromagnetic insulator MnF2. In the squeezed state, the fluctuations of the magnetization of a crystallographic unit cell vary periodically in time and are reduced below that of the ground-state quantum noise.

Coupled electron-phonon modes in optically pumped resonant intersubband lasers.

Intersubband lasing at 12-16 microm based on a CO2 laser pumped stimulated resonant Raman process in GaAs/AlGaAs three-level double-quantum-well structures is reported. The presence, or lack of, lasing action provides evidence for resonantly coupled modes of collective electronic intersubband transitions and longitudinal optical phonons. An anticrossing behavior of these modes is clearly seen when the difference between the pump and lasing energies (i.

Spin-wave quantization in ferromagnetic nickel nanowires.

The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires.

Ordering and self-organization in nanocrystalline silicon.

The spontaneous formation of organized nanocrystals in semiconductors has been observed during heteroepitaxial growth and chemical synthesis. The ability to fabricate size-controlled silicon nanocrystals encapsulated by insulating SiO2 would be of significant interest to the microelectronics industry. But reproducible manufacture of such crystals is hampered by the amorphous nature of SiO2 and the differing thermal expansion coefficients of the two materials.