Magnetic structure and properties of the honeycomb antiferromagnet [Na(OH)]Mn(NCS).

We report the magnetic structure and properties of a thiocyanate-based honeycomb magnet [Na(OH)]Mn(NCS) which crystallises in the unusual low-symmetry trigonal space group 3̄. Magnetic measurements on powder samples show this material is an antiferromagnet (ordering temperature = 18.1(6) K) and can be described by nearest neighbour antiferromagnetic interactions = -11.

2D Time-Domain Spectroscopy for Determination of Energy and Momentum Relaxation Rates of Hydrogen-Like Donor States in Germanium.

We present measurements of the coherence times of excited states of hydrogen-like arsenic impurities in germanium (Ge:As) using a table-top two-dimensional time-domain spectroscopy (2D-TDS) system. We show that this laboratory system is capable of resolving the coherence lifetimes of atomic-like excited levels of impurity centers in semiconductors, such as those used in solid-state quantum information technologies, on a subpicosecond time scale. By fitting the coherent nonlinear response of the system with the known intracenter transition frequencies, we are able to monitor coherent population transfer and decay of the transitions from the 2p and 2p states for different low excitation pulse fields.

Photoconductive arrays on insulating substrates for high-field terahertz generation.

We report on the design, fabrication and characterisation of large-area photoconductive THz array structures, consisting of a thin LT-GaAs active region transferred to an insulating substrate using a wafer-scale bonding process. The electrically insulating, transparent substrate reduces the parasitic currents in the devices, allowing peak THz-fields as high as 120 kV cm to be generated over a bandwidth >5 THz. These results are achieved using lower pulse energies than demanded by conventional photoconductive arrays and other popular methods of generating high-field THz radiation.