Robin Nicholas

Abstract:

We present a magnetotransport study of Stark quantised InAs/GaSb superlattices at low temperatures. Analysis of magnetotransport resonances identifies a series of Stark magnetophonon resonance (SMPR) features in which a triple resonance of Bloch energy, cyclotron energy and longitudinal optic phonon energies is realised.

Abstract:

The temperature dependence of the photoluminescence intensity from frozen single walled carbon nanotube solutions is reported. This is modelled assuming that it is dominated by the small energy splitting between the dark and bright states of the singlet excitons which are found to be in the region of 1-5 meV for nanotubes of 0.8-1.2nm. The luminescence is strongly enhanced by a magnetic field along the tube axis due to the mixing of the different valley states of the excitons.

Abstract:

We report studies of the modification of the band structure of single-walled carbon nanotubes through encapsulation of the inorganic material manganese ditelluride (Mn Te2). Using photoluminescence excitation mapping we show that this leads to a global reduction of their first and second band gap energies by a similar percentage (up to 3.8%). We interpret this as due to the additional screening which causes a change in the internal dielectric constant and a possible lowering of the carbon-carbon transfer integrals. The shifts increase with increasing tube diameter due to the increased quantity of filled materials. © 2006 The American Physical Society.