Holography and Topological Semimetals

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Weyl semimetals (WSMs) are a recently discovered class of materials featuring an exotic array of properties, with potential applications including the building of novel electronic devices. The electrons in some WSMs interact strongly with one another, making their theoretical study challenging. One tool for modelling strongly interacting systems is holography, also known as the anti-de Sitter/conformal field theory correspondence. Holography has been used to model WSMs before, but there are open problems to do with holographically describing important features of real WSMs. In this project I will develop a new generation of holographic models and techniques, capable of addressing several of these problems: 1. The effects of imperfections in a WSM’s crystal structure on its electronic properties, particularly when the imperfections cause the electrons experiencing an effective curved spacetime. 2. Certain non-trivial physics that occurs at the boundaries of WSMs, partly arising due to their topological properties. 3. Holographically modelling a WSM with equations that are invariant under time reversal, as is the case for the equations describing many real WSMs. The project will be carried out at Nordita, a joint department of Stockholm University (SU) and KTH Royal Institute of Technology. The supervisor, Alexander Krikun, is an expert in holographic approaches to condensed matter physics. Through the research and training in the project I will obtain new skills, such as numerical techniques for solving boundary value problems in partial differential equations. SU and KTH both have condensed matter theory groups researching WSMs, from which I will gain expertise in non-holographic methods. The project includes a secondment at Instituto de Física Teórica-CSIC/UAM in Madrid, with a group with expertise in anomalous transport, an important aspect of WSM physics. This secondment will support the research and training, and foster new international collaborations.