Fermi surface instabilities and quantum order at high pressure

Lead Research Organisation: Royal Holloway University of London
Department Name: Physics

Abstract

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Description 1) First observation of the electronic Fermi surface and effective carrier mass in the correlated metallic state on the threshold of Mott localisation. This required high frequency tank circuit measurements on the Mott insulator NiS2, which was metallised in a pressure device at about 40,000 atmospheres. 2) Discovery of unconventional superconductivity in the layered iron-germanide YFe2Ge2. This material shares key structural and electronic characteristics of the high temperature superconducting iron pnictides and chalcogenides, but is the first example of an iron-based unconventional superconductor outside those families of materials. 3) Discovery and investigation of the structural quantum critical point in the cage compounds (Ca/Sr)3(Ir/Rh)4Sn13. These complex materials undergo superlattice formation on cooling. It is possible to reduce the superlattice transition temperature towards zero, either by changing the chemical composition or by applying hydrostatic pressure. In the vicinity of the critical point, where the superlattice transition temperature extrapolates to zero Kelvin, superconductivity is enhanced and soft lattice vibrations cause an unconventional temperature dependence of the electrical resistivity as well as enhancing the specific heat capacity. 4) First observation of ferromagnetic quantum critical point masked by spin density wave order at zero field in Nb1-yFe2+y. To detect the very small spin density wave ordered moments highly sensitive neutron diffraction measurements have been required. Inelastic neutron scattering measurements have revealed low-energy excitations in considereable ranges of reciprocal space reflecting the system's proximity to different magnetically ordered states.
Exploitation Route They have already motivated further fundamental research. The techniques developed for the high pressure work on NiS2 can now be applied to similar, challenging experiments in other materials. The improved understanding of a structural quantum critical point will have implications for the investigation and exploitation of structure-property relations, in particular in thermoelectrics. The discovery of a new unconventional superconductor adds a fresh perspective in the endeavour to understand and master pairing mechanisms that can lead to robust superconductivity at elevated temperatures.
Sectors Electronics
 
Description Please see the impact description provided for EP/K012894/1.
Sector Aerospace, Defence and Marine,Electronics,Energy
Impact Types Economic
 
Description Diamond - matched Studentship (2011)
Amount £31,367 (GBP)
Organisation Diamond Light Source 
Sector Private
Country United Kingdom
Start 09/2011 
End 08/2014
 
Description Diamond - matched Studentship (2013)
Amount £33,239 (GBP)
Organisation Diamond Light Source 
Sector Private
Country United Kingdom
Start 09/2013 
End 08/2016
 
Description RHUL - Crossland (2011)
Amount £31,367 (GBP)
Organisation Royal Holloway, University of London 
Sector Academic/University
Country United Kingdom
Start 09/2011 
End 08/2014
 
Description RHUL - Crossland (2013)
Amount £33,239 (GBP)
Organisation Royal Holloway, University of London 
Sector Academic/University
Country United Kingdom
Start 09/2013 
End 08/2016
 
Description RHUL College SEPnet Scholarship
Amount £60,000 (GBP)
Organisation Royal Holloway, University of London 
Sector Academic/University
Country United Kingdom
Start 10/2016 
End 09/2019
 
Description RHUL - Cambridge 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution experiments at large facilities and at extreme conditions
Collaborator Contribution sample provision and experiments at low temperatures, high fields and moderate pressures
Impact study of novel superconductors
Start Year 2007
 
Description RHUL - Diamond 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution University Lab based experiments at extreme conditions
Collaborator Contribution Synchrotron X-ray experiments at extreme conditions
Impact comprehensive measurements under extreme conditions
Start Year 2011
 
Description RHUL - Hefei 
Organisation University of Science and Technology of China USTC
Department Hefei National Laboratory for Physical Sciences at the Microscale
Country China 
Sector Charity/Non Profit 
PI Contribution experiments at extreme conditions
Collaborator Contribution sample provision
Impact study of novel superconductors
Start Year 2010
 
Description RHUL - TU Munich 
Organisation Technical University of Munich
Country Germany 
Sector Academic/University 
PI Contribution neutron scattering experiments
Collaborator Contribution sample provision; travel support
Impact study of new electronic states of matter and magnetic quantum critical phenomena
Start Year 2007
 
Description RHUL - TU Vienna 
Organisation Vienna University of Technology
Country Austria 
Sector Academic/University 
PI Contribution experiments at extreme conditions
Collaborator Contribution sample provision
Impact study of novel superconductors
Start Year 2011