Condensed matter

Condensed matter research at the University of Leeds

We focus on experimental work centred on spintronics, in particular we fabricate nanostructures from a variety of materials and investigate their properties as a function of structure, temperature and magnetic field.

We are particularly interested in electron transport in novel structures and materials. One of our strengths is our ability to fabricate a wide range of structures including spin-valves, tunnel junctions, ferromagnet/superconductor junctions and quantum point contacts for Andreev scattering. Structures are produced using, for example, shadow masks, MBE for self-organisation, lithography, templates and FIB processing. We characterise these structures using neutron and x-ray scattering, AFM/STM and magnetometry.

Our research

Magnetism and magnetic nanostructures
There is an extensive programme of work on magnetic materials in ultrathin film form, and we are exploring other methods of nanostructuring these materials to make interesting devices. We have a substantial body of work on spin-valves and giant magnetoresistance, and this has led naturally to research on other spintronic devices that involve tunnel junctions and spin injection into semiconductors. We also work on the magnetic properties of the various parts of the devices that include magnetically biasing the reference layers, the polarisation presented at an interface by a magnetic layer and its dependence on material parameters such as roughness and intermixing.

Carbon based spintronics
Our research on carbon materials focusses on carbon nanotubes and graphene. Carbon exists in many allotropic forms, but these two materials provide naturally-occurring examples of low-dimensionality combined with high crystalline purity, allowing access to several exotic quantum phenomena. As components in the types of device used in spintronics research carbon nanotubes and graphene both offer long spin coherence times, meaning that information encoded using the spin on an electron can be retrieved from a device following processing. The lack of scattering in carbon nanotubes also makes them viable components in more advanced quantum information devices, where electrons are entangled. We fabricate nanoscale devices in order to access these quantum phenomena.

Spintronics for quantum information processing
One of the long-term directions that spintronics can grow in is the area of quantum information, as electron spins are canonical two-level quantum systems that are promising candidates for scalable qubits in a solid-state architecture. There are many aspects of quantum information that condensed matter physics can address: coherence, entanglement, fabrication of nanoscale elements and the communication between them, to name but a few. Many proposed schemes have in common the fabrication of nanostructures and communication links that incorporate a method of quantum control. We are exploring the application of spintronics and novel materials, such as CNTs or graphene, to quantum information. Spintronics experiments require a high degree of sophistication in materials growth, nanoscale fabrication and sample characterisation.

Facilities

We are developing our research portfolio to focus on these aspects, and this is reflected in our extensive suite of facilities.

Materials growth
We have world-class facilities for the deposition of thin films including metals, oxides and semiconductors. In particular, we specialise in the growth of magnetic multilayers for spintronic applications. The thin films are grown via physical vapour deposition (PVD) processes namely sputtering, molecular beam epitaxy and evaporation. In addition to PVD we also produce layers of organic materials including C60 and epitaxial graphene.

Fabrication
We make use of the University's Wolfson cleanrooms that are located in the School of Electronic and Electrical Engineering. The cleanroom has facilities for photolithography, electron-beam lithography and focused-ion-beam lithography as well as standard wet and dry etching processes. In addition, we have a Nanoprobe system containing an SEM column and four scanning probe tips.

Sample characterisation
The samples produced in the group require sophisticated measurement techniques. We determine the electrical, structural and magnetic properties of our samples over a range of temperatures and magnetic fields. We utilise a range of facilities related to transport measurements, magnetometry, structural characterisation and microscopy.

Links with industry

We have a broad research portfolio that has the potential to be exploited in commercial application. We provide opportunities for collaborative research and development and access to the world-class facilities and expertise available within the group. We specialise in the deposition and characterisation of thin-film coatings, and their subsequent patterning into nanoscale structures for device application. We provide a tailored material growth service including the design, fabrication and analysis of thin films and devices, and access to an extensive range of characterisation equipment. We welcome applications for collaborative research and development projects and can provide access to external funding.

Further information

Visit our condensed matter research group website.

PhD projects

We have opportunities for prospective PhD students. Potential projects can be found in our postgraduate research opportunities directory.