Coherent two-dimensional Fourier transform spectroscopy using a 25 Tesla resistive magnet.

We performed nonlinear optical two-dimensional Fourier transform spectroscopy measurements using an optical resistive high-field magnet on GaAs quantum wells. Magnetic fields up to 25 T can be achieved using the split helix resistive magnet. Two-dimensional spectroscopy measurements based on the coherent four-wave mixing signal require phase stability. Therefore, these measurements are difficult to perform in environments prone to mechanical vibrations. Large resistive magnets use extensive quantities of cooling water, which causes mechanical vibrations, making two-dimensional Fourier transform spectroscopy very challenging. Here, we report on the strategies we used to overcome these challenges and maintain the required phase-stability throughout the measurement. A self-contained portable platform was used to set up the experiments within the time frame provided by a user facility. Furthermore, this platform was floated above the optical table in order to isolate it from vibrations originating from the resistive magnet. Finally, we present two-dimensional Fourier transform spectra obtained from GaAs quantum wells at magnetic fields up to 25 T and demonstrate the utility of this technique in providing important details, which are obscured in one dimensional spectroscopy.

Biexcitons in monolayer transition metal dichalcogenides tuned by magnetic fields.

We present time-integrated four-wave mixing measurements on monolayer MoSe2 in magnetic fields up to 25 T. The experimental data together with time-dependent density function theory calculations provide interesting insights into the biexciton formation and dynamics. In the presence of magnetic fields the coherence at negative and positive time delays is dominated by intervalley biexcitons. We demonstrate that magnetic fields can serve as a control to enhance the biexciton formation and help search for more exotic states of matter, including the creation of multiple exciton complexes and excitonic condensates.

Oligodeoxyadenylate stimulates the protein kinase activity of anti-DNA sIgA from human milk.

Preparations of anti-DNA sIgA were obtained from human milk by sequential chromatography on protein A-sepharose, DEAE-fractogel and DNA-cellulose. The influence of oligonucleotides on protein kinase activity was investigated. It was discovered that incubation of anti-DNA sIgA with oligodeoxyriboadenylate d(A)12 stimulates the phosphorylation of polypeptides of sIgA in the presence of [gamma-32P]ATP. The greatest was the incorporation of P into the sIgA H-chains. We also demonstrated stimulation of the casein kinase activity of anti-DNA sIgA by d(A)12. The stimulation of the protein kinase activity of anti-DNA sIgA by oligoriboadenylate r(A)12 was not detected.