Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.820929
Title: Phase transitions in two-dimensional itinerant electron systems
Author: Trott, Matthew J.
ISNI:       0000 0004 9357 2461
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2020
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Abstract:
The aim of this thesis it to contribute to three open problems in the theory of itinerant electron systems in two spatial dimensions. Firstly, the mechanism for charge density wave formation in the transition metal dichalcogenides is a debated subject. In this thesis it is shown that charge density wave formation is possible via a purely electronic mechanism in monolayer vanadium diselenide. The competition of superconductivity and density wave formation is taken into account using the renormalisation group. As the Fermi surface is tuned to perfect nesting, a charge density wave phase emerges when the Heisenberg exchange interaction is of the order of the contact Coulomb repulsion. Secondly, the search for materials which exhibit topological superconductivity is ongoing. Possible candidates are strongly spin-orbit-coupled metals. In this thesis a square-lattice Hubbard model with strong Rashba spin-orbit coupling and one of the Fermi surfaces close to a Lifshitz transition is examined. The metal is shown to be generically unstable to the formation of mixed-parity superconductivity with a helical triplet component via a renormalisation group analysis. Thirdly, the breakdown of Fermi liquid theory close to a quantum critical point is still not well understood. In this thesis a functional renormalisation group analysis is presented using a soft frequency cutoff, investigating a general class of Pomeranchuk instabilities with Nb flavours of boson. At small Nb the theory is characterised by weakly non-Fermi-liquid behaviour of the electrons and z ≈ 2 dynamics for the order parameter fluctuations. For large Nb, the theory crosses over to z ≈ 1 scaling and non-Fermi-liquid behaviour.
Supervisor: Hooley, Chris Sponsor: Engineering and Physical Sciences Research Council (EPSRC) ; Scottish Doctoral Training Centre in Condensed Matter Physics (CM-CDT)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.820929  DOI: Not available
Keywords: Condensed matter physics ; Phase transitions ; Renormalisation group ; Strongly correlated electrons ; Superconductivity ; Charge density waves ; QC173.458E43T8 ; Condensed matter ; Phase transformations (Statistical physics)
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