Electrical injection of THz spin excitations in topological solid state devices

To support the future growth of the digital economy, we must explore computing paradigms that overcome the inherent limitations of semiconductors. A proposed way to do this is to use the spin of electrons to carry information: a field known as spintronics. This technology promises to provide a route to low power, high speed computers of the future. An emerging area within spintronics is Terahertz spintronics, where interactions between electrons at trillionths of a second are used. This is 1000 times faster than the current state of the art in silicon. To make this technology work, we need to find ways to inject and control THz spin currents into materials. This project will try to accomplish this using low-temperature deposited Gallium Arsenide (LT GaAs) and topological insulators, materials with a graphene like surface state that can efficiently transport and control spin. The successful student will learn state-of-the-art cleanroom techniques that are currently used in the semiconductor industry, low-temperature measurement techniques widely used in the development of quantum computers, and materials growth relevant to next generation computing technology; all while performing cutting edge research in a world leading THz group.

<p>To support the future growth of the digital economy, we must explore computing paradigms that overcome the inherent limitations of semiconductors. Spintronics seeks to build novel devices for computing and communications that utilise electron spin. Applications include low power electronics, high speed logic, neuromorphic computing and novel memory devices. [1-3] Cutting edge research in this area focuses on the high-speed interactions between spins, which allow spintronic devices to operate at THz frequencies, more than 1000 times faster than the current state of the art in silicon. [4] However, integration of spintronics with conventional electronics is extremely challenging, due to the inherent difficulty of converting magnetic and spin excitations into electrical currents. A promising approach is to utilise spin orbit effects at interfaces. [5]</p> <p>Topological Insulators (TIs) are materials with strong spin-orbit interactions that are semiconducting in the bulk but with conducting surface states. The spin-momentum relationship of the high mobility surface states also provides a route to high-speed spin-charge conversion. [6] To utilise these interfaces, they must be integrated with a THz source in a solid state device. Low Temperature GaAs (LT-GaAs) is a commonly used source of THz radiation. [7] While some initial research has suggested LT GaAs can be integrated with topological materials, heterostructures and devices utilising these materials have yet to be comprehensively understood. [8] This project will develop LT GaAs injectors for the study of the THz spin response of TI devices, using a range of facilities including ultra-low temperature dilution refrigerator facilities.</p> <p>University of Leeds is a world leader in the growth of both high-quality Bi2Se3/BiInSe topological insulator multilayers utilising the Royce Deposition System and the growth of LT-GaAs, grown on dedicated III-V MBE growth chambers. As a post graduate researcher on this project you will be involved in the cleanroom fabrication, electrical and optical characterisation, and simulation of these novel materials and devices.  These techniques will be combined to develop LT-GaAs/TI heterostructures with electrically injected, amplified, tuneable THz spin dynamics for future computing and communications technology.</p> <p>[1] – S D Bader and S S P Parkin, Annu. Rev. Condens. Matter Phys. 1, 1, 2010.</p> <p>[2] – C H Marrows et al, NPJ Spintronics, 2, 12, 2024.</p> <p>[3] – S S P Parkin et al, Science, 320, 5873, 2008.</p> <p>[4] – J Walowski and M Munzenberg, Jour of Appl Phys. 120, 14, 2016.</p> <p>[5] – M Tong et al, Nano Letters, 21, 1, 2020.</p> <p>[6] – P Di Pietro et al, Nat Nano. 8, 556 – 560, 2013.</p> <p>[7] – M C Beard et al, Jour Appl. Phys. 90, 12, 2001.</p> <p>[8] – M Eddrief et al, Nanotechnology, 25, 245701, 2014</p>

<p>Formal applications for research degree study should be made online through the <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University's website</a>. Please state clearly in the Planned Course of Study section that you are applying for <em><strong>EPSRC DTP Engineering & Physical Sciences</strong></em> (if you do not apply to this programme code, your application will not be considered) and in the research information section that the research degree you wish to be considered for is <em><strong>Electrical injection of THz spin excitations in topological solid state devices</strong></em> as well as <a href="https://eps.leeds.ac.uk/physics/staff/9991/timothy-moorsom">Dr Timothy Moorsom</a> as your proposed supervisor. <em><strong>Please state clearly in the Finance section that the funding source you are applying for is School of Electronic & Electrical Engineering Studentship 2025/26.</strong></em></p> <p>If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p style="margin-bottom:11px">Applications will be considered after the closing date.  Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application.  We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p style="margin-bottom:11px">Please note that you must provide the following documents in support of your application by the closing date of Friday 28 February 2025:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p class="MsoNoSpacing">A highly competitive EPSRC Doctoral Landscape Award providing full academic fees, together with a tax-free maintenance grant at the standard UKRI rate (£19,237 in academic session 2024/25) for 3.5 years.  Training and support will also be provided.</p> <p>This opportunity is open to all applicants.  All candidates will be placed into the EPSRC Doctoral Landscape Award Competition and selection is based on academic merit.</p> <p><strong>Important:</strong> Please note that that the award does <em><strong>not</strong></em> cover the costs associated with moving to the UK.  All such costs (<a href="https://www.leeds.ac.uk/international-visas-immigration/doc/applying-student-visa">visa, Immigration Health Surcharge</a>, flights etc) would have to be met by yourself, or you will need to find an alternative funding source. </p> <p>Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p>

<p>For further information about this project, please contact Dr Timothy Moorsom by email to <a href="mailto:t.moorsom@leeds.ac.uk">t.moorsom@leeds.ac.uk</a></p> <p>For further information about your application, please contact PGR Admissions by email to <a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p>