Dr Dharmalingam Prabhakaran

Abstract:

All-optical control of terahertz pulses is essential for the development of optoelectronic devices for next-generation quantum technologies. Despite substantial research in THz generation methods, polarisation control remains difficult. Here, we demonstrate that by exploiting bandstructure topology, both helicity-dependent and helicity-independent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. We show that narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarisation. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21 – 1.40 THz as the angle is tuned from 15° - 45°. We therefore present Cd3As2 nanowires as a promising novel material platform for controllable terahertz emission.

Abstract:

The deposited package contains experimental single crystal inelastic neutron scattering data probing the spin dynamics in the quantum Ising chain magnet CoNb2O6 in applied transverse magnetic field together with corresponding theoretical calculations of the spin dynamics. A matlab script to read and plot all data in ASCII files is also supplied.

Abstract:

The magnetic susceptibility χ of RMnO3 (R = La, Y) manganites was measured for paramagnetic phase as a function of the hydrostatic pressure P up to 2 kbar at some fixed temperature in the range from 78 to 300 K. A pronounced magnitude of the pressure effect dlnχ/dP was found to be positive in sign for LaMnO3 and negative for YMnO3, both being strongly temperature dependent. Analysis of the experimental data, based on the Curie-Weiss behavior of χ(T), allowed to estimate the pressure derivative of the paramagnetic Curie temperature to be dΘ/dP = (0.25 ± 0.03) and −(2.4 ± 0.4) K/kbar for LaMnO3 and YMnO3, respectively.