Project description (C.J. Nuttall):

The quest for novel nano-composite materials has a wide scope and also includes materials in which the electronic ground state supports superconductivity. The advantages of nano-composite superconducting materials would be the incorporation of secondary physical properties from the composite, with superconductivity. Possibilities include advantages in material processing and also combinations of superconductivity with exotic physical behaviors, e.g. magnetism. The approach used in this work involves the synthesis of novel host materials that become superconducting upon intercalation and the development of their intercalation chemistry.

In the present investigation we are focussing on a novel layered intercalation system A_xMNX {A = intercalated species; M = Zr, Hf; X = halogen atom Cl, Br, I}. The host material MNX is semi-conducting and the ground state is changed to superconductivity concomitant with the intercalation of electron donating species. This has been achieved where A = alkali metal ion and yields intercalated materials exhibiting a variety of superconducting transition temperatures; e.g. Li_0.16ZrNCl (T_c = 15K) and Li_x(THF)_yHfNCl (T_c = 25.5K). By developing the intercalation chemistry of these materials it will be possible to design nano-composite superconducting materials with appropriate functionality.

A further aim of this work is a full physical property investigation of the new materials, which will allow the correlation of structural parameters with those of physical property. The investigation will also involve correlations as a function of pressure (both chemical and physical), and will lead to a full understanding of the materials electronic phase diagram.