Engineering novel ground states and excitations in quantum spin liquids

Dr David Boldrin

The 40 year search for Quantum Spin Liquids (QSLs) is a cornerstone of condensed matter physics [1]. QSLs are novel states of matter that are the magnetic analogue of liquids; their magnetic moments remain fluctuating and never order. In addition, quantum effects mean these fluctuations persist even at zero temperature, leading to exotic emergent phenomena. Originally predicted to underpin high temperature superconductivity [2], the elusive search for QSLs has serendipitously led to some of the most groundbreaking discoveries in fundamental condensed matter physics [3,4]. Up to now, the search for QSLs is limited by the lack of model materials to study, the difficulty in making them and the challenges posed by characterising them. This project will build on our recent work addressing these bottlenecks by synthesising high quality samples of a recently discovered QSL model system and characterising its properties primarily with state-of-the-art neutron scattering techniques at national facilities across Europe..

The project is part-funded by the Institut Laue-Langevin (ILL in Grenoble, France), the world's flagship for neutron science, and will be split 50:50 between the University of Glasgow (UoG) and the ILL. Supervision at the ILL will be lead by Dr. Björn Fåk, principal scientist on the PANTHER beamline. At UoG, the project will involve synthesis of model QSL systems and advanced characterisation using X-ray diffraction, SQUID magnetometry and electron microscopy within the Materials and Condensed Matter Physics (MCMP) group at UoG. At ILL, focus will be on performing and analysing cutting-edge neutron scattering experiments in order to probe the fundamental structure and excitations of these QSL candidates.

Please contact David Boldrin as soon as possible to discuss the project if it is of interest to you.

[1] C. Broholm et al., Science 367, 263 (2020).
[2] P. W. Anderson, Science 235, 1196 (1987).
[3] T.-H. Han et al., Nature 492, 406 (2012).
[4] Physics World, Electron’s dual nature appears in a quantum spin liquid, 2021

Using electrons to fabricate magnetic nano-circuits

Dr Trevor Almeida

Next generation scanning electron microscopes have to ability to inject precursor gases for the fabrication of magnetic structures with dimensions as small as ~ 10 nm, called focused electron beam induced deposition (FEBID). Alteration of the electron-beam scan conditions during decomposition of the injected gases provides effective control over the composition, size and morphology of the deposited magnetic material. FEBID can be used to construct nano-scale circuits with complex geometries that provide interesting positions and paths for magnetic domain walls, which can be driven by application of current pulses and magnetic fields.

This project will be supervised by Dr Trevor Almeida, Lecturer in the Materials and Condensed Matter Physics group. The project will focus on fabricating nano-scale circuits using FEBID and characterising their chemical, structural and magnetic properties using advance electron microscopy techniques. In particular, focus will be placed on how joule heating / annealing affects the saturation magnetisation and domain wall motion through the FEBID structures. Another aspect would be optimising the magnetic imaging techniques for live imaging of dynamic magnetism within the nano-circuits. There will also be opportunities to take part in collaborative experiments at the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons in Jülich.

Pressure-dependent synchrotron studies of barocaloric materials for zero carbon heating and cooling

Dr David Boldrin

Applications are open for a fully-funded PhD studentship in the field of “Pressure-dependent synchrotron studies of barocaloric materials for zero carbon heating and cooling" to start in October 2023. It is a collaborative effort (50:50) between Diamond Light Source and the University of Glasgow. The work is led by Dr. David Boldrin in the Materials and Condensed Matter Physics group (School of Physics and Astronomy) at Glasgow and Dr Eamonn Connolly on the I11 beamline at Diamond. The studentship will develop novel instrumentation for use with synchrotron radiation in order to study cutting-edge energy materials.

Heating and cooling result in over a third of the UK’s CO2 emissions and decarbonising these essential systems is imperative to reach the legal obligation of net-zero carbon by 2050 [1]. Barocalorics, materials that undergo large temperature changes under an applied pressure, are a promising technology to achieve this goal [2,3,4]. The challenge now is to tune these barocaloric effects away from the often-large operational hydrostatic pressures (>2.5 kbar), towards the low pressures (<1 kbar) required for a commercially competitive heating or cooling device. In order to do this, precise structure-pressure relationships of barocaloric materials in the 0-2kbar hydrostatic pressure range are required, yet this capability is currently lacking using synchrotron X-ray powder diffraction (SXPD). This project will build a medium pressure cell (0-2 kbar) on the I11 high-resolution powder diffraction beamline at Diamond Light Source and use it to study the pressure-temperature phase diagram of state-of-the-art barocalorics.

Early applications are advised as the position will be filled once a suitable candidate has been identified. Further information on the project, with details on how to apply, can be found at the following websites:

https://www.diamond.ac.uk/Careers/Students/Studentships/2023-projects/2023-STU0474.html

https://www.findaphd.com/phds/project/phd-in-physics-pressure-dependent-synchrotron-studies-of-barocaloric-materials-for-zero-carbon-heating-and-cooling/?p155125

[1] Clean Growth - Transforming Heating, BEIS, (2018). https://www.gov.uk/government/publications/heat-decarbonisation-overview-of-current-evidence-base
[2] B. Li et al., Nature 567, 506 (2019).
[3] D. Boldrin, Appl. Phys. Lett. 118, 170502 (2021).
[4] https://www.royce.ac.uk/materials-for-the-energy-transition-caloric-energy-conversion/

Development of nanostructured half-Heuslers for thermoelectric waste heat recovery

Dr Donald MacLaren

Thermoelectric materials convert waste heat into useful electric power. Even inefficient thermoelectric power generation recovery can have a substantial impact on energy consumption because more than half of primary energy is ultimately wasted as heat. So far, thermoelectric generators (TEGs) have been restricted to niche applications, such as powering the Voyager space probes, where durable, reliable and low-maintenance power generation is essential. However, the market for thermoelectric energy harvesters is projected to approach $1bn within a decade. Potential applications for TEGs include scavenging heat from car exhausts, producing combined heat and power units for use in remote, off-grid locations, and replacing batteries in wearable microelectronic devices. A major limitation has been to develop cheap, efficient TEGs that do not rely on toxic or scarce resources. This project aims to develop a viable, non-toxic alternative to lead telluride TEGs, using 'Heusler alloys', which combine abundant elements such as titanium, nickel and tin. It builds on recent advances in Heusler alloy synthesis made in collaboration with Dr. Jan-Willem Bos of Heriot Watt University and we now aim to build a commercially-viable prototype device. The project will involve substantial electron microscopy in order to correlate nanostructural details with thermoelectric performance; it will also involve the use of national facilities for neutron and electron scattering studies; and there are substantial opportunities for industrial engagement.

Atomic structures of optical coatings for ultrahigh-precision interferometry

Tantala model

Dr Ian MacLaren and Prof Sheila Rowan

Various applications rely on ultrahigh precision interferometry including laser stabilisation and frequency stabilisation, laser gyroscopes for intertial guidance systems, quantum optical devices, and most especially, the gravitational wave interferometers used in the recent discovery of gravitational waves, binary black-hole mergers and neutron star mergers. One of the limitations on such interferometry is due to thermal noise in the amorphous optical coatings used in the multilayer mirrors at the ends of the interferometer arms. If this noise could be reduced, then the sensitivity of the interferometers can be further improved allowing better gravitational wave detection for a larger fraction of the universe.  This thermal noise originates in atomic-scale processes which are poorly understood and to improve the materials requires an understanding of structures and dynamics at the atomic scale. This project will then focus on using cutting edge techniques in electron microscopy to provide information about the structure and chemistry of these coatings on sub-nanometre length scales combined with density functional theory and molecular dynamics simulation work focused on understanding the atomic structure and dynamics of these amorphous materials. This work will involve extensive interaction with the Institute for Gravitational Research at the University of Glasgow, as well as with academic researchers at other UK Universities; Stanford University, California; and other Universities worldwide.

Xe-beam microscopy and specimen preparation

Dr Ian MacLaren, Dr Donald MacLaren

Focused Xe beams can be used to sculpt materials in all sorts of ways.  This project will use a newly installed DualBeam instrument with a Xe and an electron beam to develop methods for the preparation of ultrahigh quality samples for electron microscopy, as well as for the 3D imaging of the structure, chemistry and crystallography of materials and devices.  You will make a major contribution to the commissioning of this exciting new instrument in collaboration with the manufacturers of the instrument, partners from other Schools at the University of Glasgow, and from other universities and research institutes.

Pulsed laser deposition of advanced oxide materials for data-storage applications

Pulsed Laser Deposition

Dr Donald MacLaren

As part of a major new investment, the Kelvin Nanocharacterisation Centre recently installed a pulsed laser deposition system for the fabrication of a variety of thin film devices and coatings. The pulsed laser deposition technique is almost ideal for depositing the complex, multi-component materials now being proposed by theorists as being essential to the next generation of microelectronic devices. However, even atomic-scale defects, dislocations, impurities and strain can impair performance and the optimal fabrication conditions are simply unknown in most cases. This project will use the new deposition system and will characterise the nanometric structure of a variety of multi-component oxide materials for technological applications. A particular focus is the development of oxide-based devices for data storage applications. A combination of electron diffraction, scanned probe microscopies and transmission electron microscopy will be used to characterise the samples and the student will gain highly-transferable skills in materials deposition and high resolution characterisation. The project will suit students with an interest in instrumentation and chemical physics and has the opportunity for collaboration with a number of national and international partners.