Microwave Measurements

Microwave measurements of surface impedance probe properties as a function of temperature and frequency. This provides a powerful tool to investigate electron dynamics of normal and superconducting states, where the properties are strongly dependent on the superconducting order parameter. Our work has included studies of many interesting materials such as the Cuprate, Heavy fermion, Ruthenates and currently we are working on Organic superconductors.

Microwave Facility

We have developed a novel hollow dielectric resonator technique for extracting important information from microwave measurements. By measuring the change in resonant frequency of the cavity, as the temperature of the sample is changed, we can measure the magnetic penetration depth in the sample. This provides information about the number of superconducting electrons. The losses within the cavity provide information about the excitations in a superconductor. This can be related to the theoretical predictions of microscopic models.

Members of Microwave Group

Prof. Colin Gough
Dr Rod Ormeno
Mr Phil Baker

Selected Publications:

CE Gough, RJ Ormeno, AD Sibley, M Hein, S Nishizaki, Y Maeno. 2002. Microwave spectroscopy of novel superconductors, Journal of Physics and Chemistry of Solids, 63, 12, 2187-2193. Publication: 9845.

RJ Ormeno, AD Sibley, CE Gough, S Sebastian, IR Fisher. 2002. Microwave conductivity and penetration depth in the heavy fermion superconductor CeCoIn₅, Physical Review Letters, 88, 4, 047005 (1-4). Publication: 9852.

RJ Ormeno, CE Gough, JJ Wingfield, G Yang. 2000. Probing antiferromagnetism in GdBa₂Cu₃O_7-_p using surface impedance, Physica. B, Condensed matter, 284, 913 - 914. ISSN: 0921-4526.

JR Powell, A Porch, AP Kharel, MJ Lancaster, RG Humphreys, F Wellhofer, CE Gough. 1999. The nonlinear surface impedance of YBa₂Cu₃0_7-delta thin films in zero and large applied fields, Journal of Physics D: Applied Physics, 86, 4, 2137 - 2145. ISSN: 0022-3727.

JR Powell, A Porch, RG Humphreys, F Wellhofer, MJ Lancaster, CE Gough. 1998. Field, temperature, and frequency dependence of the surface impedance of YBa₂Cu₃O₇ thin films, Physical Review B, Condensed Matter, 57, 9, 5474 - 5484. ISSN: 0094-0003.

CE Gough, A Porch, MJ Lancaster, JR Powell, B Avenhaus^*, JJ Wingfield, D Hung^*, RG Humphreys^*. 1997. High Tc co-planar resonators for microwave applications and scientific studies, Physica. C, Superconductivity, 282, 1, 395 - 398. ISSN: 0921-4534.

JR Powell, A Porch, MJ Lancaster, RG Humphreys, CE Gough. 1997. Hysteretic microwave measurements of YBCO thin films in small swept applied fields, Institute of Physics Conference Series, 158, 125 - 128. ISSN: 0537-9504.

JJ Wingfield, JR Powell, A Porch, CE Gough. 1997. Field-dependent surface impedance of YBCO single crystals and evidence for a non-zero Hall term, Physica. C, Superconductivity, 282, 3, 1597 - 1598. ISSN: 0921-4534.

JJ Wingfield, JR Powell, CE Gough, A Porch. 1997. Sensitive measurement of the surface impedance of superconducting single crystals using a sapphire dielectric resonator, IEEE Transactions on Applied Superconductivity, 7, 2, 2009 - 2012. ISSN: 1051-8223