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Fluctuation and equilibration in artificial magnetic quasicrystals

PGR-P-182

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Key facts

Type of research degree
PhD
Application deadline
Ongoing deadline
Country eligibility
International (open to all nationalities, including the UK)
Funding
Competition funded
Supervisors
Professor Christopher Marrows
Schools
School of Physics and Astronomy
Research groups/institutes
Condensed Matter
<h2 class="heading hide-accessible">Summary</h2>

Frustration is the inability of a physical system to simultaneously satisfy competing constraints. It occurs across physics and beyond, but is a particularly important topic in magnetism, a field in which (relatively) simple systems can be represented by toy statistical mechanical models that can then be extended into other fields model phenomena as diverse as forest fires and financial networks.<br /> <br /> The study of frustration in magnetism has recently been given a new lease of life since artificial frustrated systems can now be built and studied using nanotechnology: in the case of magnetism, this is done by constructing arrays of magnetic nanoelements arranged in patterns where their magnetostatic interactions are frustrated.<br /> <br /> The advantages of this approach is that it is possible to build experimental realisations of models that nature does not provide crystal structures for, with every parameter in the model tunable by adjusting the element size, shape, and spacing. Moreover, the microstates of these artificial statistical mechanical systems can be inspected in detail using advanced magnetic microscopy methods, including time-resolved imaging to study thermal fluctuations in those microstates.<br /> <br /> To date, almost all artificial frustrated spin systems have been crystalline in that they are periodic arrays. In particular, square and hexagonal arrays have been studied as analogs of spin ice crystals. Thermal excitations in spin ices show appear as emergent quasiparticles with many of the properties of magnetic monopoles, physics that has been reproduced in their artificial counterparts. In this project we will study quasicrystalline systems, where the magnetic nanoelements are arranged on a Penrose tiling. Whilst small parts of this pattern repeat, the whole pattern never does.

<h2 class="heading hide-accessible">Full description</h2>

<p>We have begun to study these Penrose-based systems in an athermal state [Shi et al., Nature Physics 2018, <a href="https://doi.org/10.1038/s41567-017-0009-4">https://doi.org/10.1038/s41567-017-0009-4</a>], where the energy scales are all much larger than kT and so the state of the system is frozen in. In this project we will build systems that are thermally fluctuating by tuning these energy scales towards kT. In this way we will study collective nature of the freezing and melting of the artificial spin system and seek to understand the nature of its emergent excitations.&nbsp;</p>

<h2 class="heading">How to apply</h2>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="https://www.leeds.ac.uk/info/130206/applying/91/applying_for_research_degrees">University&#39;s website</a>. Please state clearly in the research information section&nbsp;that the research degree you wish to be considered for is &lsquo;Fluctuation and equilibration in artificial magnetic quasicrystals&rsquo; as well as&nbsp;<a href="https://condensed-matter.leeds.ac.uk/people/chm/">Prof Christopher Marrows</a> as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p><em>We welcome applications from all suitably-qualified candidates, but UK black and minority ethnic (BME) researchers are currently under-represented in our Postgraduate Research community, and we would therefore particularly encourage applications from UK BME candidates. All scholarships will be awarded on the basis of merit.</em></p>

<h2 class="heading heading--sm">Entry requirements</h2>

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.

<h2 class="heading heading--sm">English language requirements</h2>

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.

<h2 class="heading">Funding on offer</h2>

<p><strong>Self-Funding Students are welcome to apply.</strong></p> <p><strong>UK</strong>&nbsp;&ndash;&nbsp;The&nbsp;<a href="https://phd.leeds.ac.uk/funding/138-leeds-doctoral-scholarships-2021-january-deadline">Leeds Doctoral Scholarship (January deadline)</a>&nbsp;and the&nbsp;<a href="https://phd.leeds.ac.uk/funding/141-henry-ellison-scholarship-2021">Henry Ellison Scholarship</a>&nbsp;are available to UK applicants. The&nbsp;<a href="https://phd.leeds.ac.uk/funding/102-bell-burnell-scholarship-award-awarded-by-the-iop">Bell Burnell Scholarship Award</a>&nbsp;is available to support applicants who are from groups that are currently under-represented in physics (awarded by the IOP).&nbsp; <a href="https://phd.leeds.ac.uk/funding/60-alumni-bursary">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p><strong>Non-UK</strong>&nbsp;&ndash; The&nbsp;<a href="https://phd.leeds.ac.uk/funding/63-school-of-physics-astronomy-fee-only-scholarship">School of Physics &amp; Astronomy Fee Only Scholarship</a>&nbsp;is available to support the additional academic fees of international applicants. The&nbsp;<a href="https://phd.leeds.ac.uk/funding/48-china-scholarship-council-university-of-leeds-scholarships-2021">China Scholarship Council - University of Leeds Scholarship</a>&nbsp;is available to nationals of China. The&nbsp;<a href="https://phd.leeds.ac.uk/funding/73-leeds-marshall-scholarship">Leeds Marshall Scholarship</a>&nbsp;is available to support US citizens. The&nbsp;<a href="https://phd.leeds.ac.uk/funding/102-bell-burnell-scholarship-award-awarded-by-the-iop">Bell Burnell Scholarship Award</a>&nbsp;is also available to international applicants and supports those who are from groups that are currently under-represented in physics (awarded by the IOP). <a href="https://phd.leeds.ac.uk/funding/60-alumni-bursary">Alumni Bursary</a> is available to graduates of the University of Leeds.</p>

<h2 class="heading">Contact details</h2>

<p>For further information regarding your application, please contact Doctoral College Admissions by&nbsp;email:&nbsp;<a href="mailto:EMAIL@leeds.ac.uk">m</a><a href="mailto:maps.pgr.admissions@leeds.ac.uk">aps.pgr.admissions@leeds.ac.uk</a>, or by telephone: +44 (0)113 343 5057</p> <p>For further information regarding the project, please contact Professor Christopher Marrows by email:&nbsp;&nbsp;<a href="mailto:C.H.Marrows@leeds.ac.uk">C.H.Marrows@leeds.ac.uk</a></p>