Electronic and Optical Materials
Conventional theories of the optical and electronic properties of materials assume electrons propagating independently in 3D crystals with a periodic array of atoms and uniform propagation of light. Many materials displaying novel or exploitable properties do not fit within these bounds. Examples include the optical properties of nanoparticles or nanoparticle assemblies, where light both scatters from the particles and induces excitations within them. Similarly, electrical conduction within low-dimensional conductors such as graphene, a single layer of carbon atoms, is far more sensitive to disorder than more typical conductors. Conventional models of material properties also ignore the strong repulsion between the constituent electrons, but for some materials these are crucial to understanding their properties. Examples include all superconductors and magnetic materials, both of which are of substantial technological and fundamental relevance. Theme 2 includes strong activity encompassing both experimental and theoretical work in these areas. Most of the work is collaborative in nature, with strong links between Theme members and across Themes, and to many international collaborators. Theory and simulation are used to inform and stimulate our experimental investigations, and indeed in many cases theoretical predictions can drive the direction of the experimental program.
Infrastructure and capability:
The MacDiarmid Institute offers access to state-of-the-art facilities across its network of researchers, which comprises a large fraction of New Zealand’s capability in advanced materials, nano-science and technology. New techniques for growth of nano-scaled or advanced materials are developed across all of the Theme 2 research objectives and systems of interest, including for example thin film deposition or production of novel ceramics. A particular Theme strength is characterisation of structural, optical, electronic, and magnetic properties via a host of techniques, including photoluminescence, calorimetry, x-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, temperature-dependent magneto-transport, magnetization, and x-ray diffraction. Equipment for all of these techniques is maintained in the laboratories of Theme 2 researchers. Significant capability has been created in the use of synchrotron techniques, including the Australian Synchrotron in which New Zealand has invested. Theory and computational work is supported by access to the BlueFern supercomputer.
A levitating magnet is repelled from a high temperature superconductor (HTS), the basis of the technology underpinning MagLev trains. Associated company HTS-110 Ltd is developing a wide range of HTS magnets and instruments for the research, energy and health sectors. A particular focus of our research is to increase the current carrying capacity of HTS wires for these applications and to develop a comprehensive understanding of the thermodynamic and physical basis for this high-current capacity.