Ultra-high conductivity oxide metals

The recent realization that the so-called delafossite oxide metals can support incredibly long low-temperature mean free paths both opens the way to the study of a host of novel transport regimes [1,2,3] and stimulates the search for other candidate ultra-high conductivity materials.  The underlying goals of the research will be both to utilize the high conductivity in novel experiments and to try to understand its origin using a combination of experiment and theory.  One avenue is to re-examine the properties of well-known high conductivity materials such as ReO3 that were first studied in an era in which far fewer experimental techniques were available than we have at our disposal today.  Another will be to investigate less widely studied candidate materials such as SrMoO3, and a third, in collaboration with the materials groups at the Institute, will be to look for more.

A single crystal of PdCoO2 focused ion beam sculpted to produce ‘wires’ with different orientations relative to the crystal axes [7]. Because of the extremely long mean free paths in PdCoO2, the resistance of the wires depends strongly on the orientation, an entirely new effect in electronic transport. The goal of this project is to investigate other potential host materials for the discovery and observation of unconventional transport on the micro- and nanoscale.

To perform the experiments, you will make use of our extensive focused ion beam (FIB) and electron beam lithography facilities, as well as the wide range of transport, thermodynamic and spectroscopic apparatus available to us. 

Paradoxically, understanding what it takes to change extremely high conductivity can be an excellent route to understanding its origin [4].  Another potential avenue of research will therefore be to take extremely clean materials and disorder them in a highly controlled way using irradiation with high energy particles at external facilities in France and elsewhere.

The project’s main goals will be fundamental understanding, but this class of work also has long-term technological potential because of the possibility of developing new classes of oxide electronics [5,6].  In performing it, you will gain first-hand experience of state-of-the-art technologies that will be of interest to future academic or industrial employers.  The project will be suitable for someone with a physics or materials science background.  A willingness to travel to beam times is another prerequisite.

References

[1] P.J.W. Moll, P. Kushwaha, N. Nandi, B. Schmidt and A.P. Mackenzie
Evidence for hydrodynamic electron flow in PdCoO2
Science 351, 1061 (2016)
[2] M.D. Bachmann, A.L. Sharpe, A.W. Barnard, C. Putzke, M. König, S. Khim, D. Goldhaber-Gordon, A.P. Mackenzie, and P.J.W. Moll
Super-geometric electron focusing on the hexagonal Fermi surface of PdCoO2
Nature Communications 10, 5081 (2019)
[3] C. Putzke, M.D. Bachmann, P. McGuinness, E. Zhakina, V. Sunko, M. Konczykowski, T. Oka, R. Moessner, A. Stern, M. König, S. Khim, A.P. Mackenzie, and P.J.W. Moll
h/e oscillations in interlayer transport of delafossites
Science 368, 1234 (2020)
[4] V. Sunko, P.H. McGuinness, C.S. Chang, E. Zhakina, S. Khim, C.E. Dreyer, M. Konczykowski, H.Borrmann, P.J.W. Moll, M. König, D.A. Muller, and A.P. Mackenzie
Controlled Introduction of Defects to Delafossite Metals by Electron Irradiation
Phys. Rev. X 10, 021018 (2020)
[5] J. Mannhart and D.G. Schlom
Oxide Interfaces—An Opportunity for Electronics
Science 327, 1607 (2010)
[6] J. Chakhalian, J.W. Freeland, A.J. Millis, C. Panagopoulos, and J.M. Rondinelli
Emergent properties in plane view: Strong correlations at oxide interfaces
Rev. Mod. Phys. 86, 1189 (2014)
[7] M.D. Bachmann, A.L. Sharpe, A.W. Barnard, C. Putzke, T. Scaffidi, N. Nandi, S. Khim, M. König, D. Goldhaber- Gordon, A.P. Mackenzie, P.J.W. Moll
Directional ballistic transport in the two-dimensional metal PdCoO2
arXiv:2103.01332

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