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Crawford, Rosemary (2019) Using graphene multilayers to transform the performance and functionality of atom chips for use in quantum sensors. PhD thesis, University of Nottingham.

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Abstract

Current atom chips, conventionally made from metal wires, suffer from anumber of different problems, which we have shown can be overcome byusing graphene conductors, specifically;

•Metal wires have a large Johnson noise due to the high carrier density.Graphene has a much lower charge carrier density(≈8 orders of magnitude lower), and thus, Johnson noise that is four orders of magnitude lower than metal. This leads to a corresponding major increase in the lifetime of the atom cloud above the wire. We have shown that an atom cloud trapped 1μm above a graphene wire has its lifetime increased by around 4 orders of magnitude compared to metal, i.e from 0.1 s to>10 minutes. This extends the Johnson noise limited lifetime so much that it becomes negligible as it is far beyond the limit imposed by the background gas collisions.

•Metal wires exert a large Casimir-Polder attraction on atoms trapped near them, thereby limiting the minimum trapping distance to 10-100μm. Using a transfer matrix method in conjunction with the Lifshitz approach, we have demonstrated that the Casimir-Polder attraction between a graphene layer and an atom is approximately 50% that of the attraction between an atom and a thin gold layer. This enables atoms to be trapped up to 2 orders of magnitude closer to a graphene atom chip and so achieve sub-micron trapping distances.

•Metal wires are spatially imperfect on 200 nm scales [1], which can lead to fragmented atom clouds. We have that shown that current lithography techniques can produce conducting paths of an arbitrary shape in graphene with roughness on only the≈10 nm scale. This leads to smoother traps and therefore smoother clouds even at sub-micron trapping distances.

•Finally, we note that graphene will also allow for a greater degree of integration between all the different components of the cold atom system, trapping wires, Ultra High Vacuum (UHV) environments and optics,thus aiding the miniaturisation of the experimental set-up.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Fromhold, T.M.
Keywords:	Graphene conductors; Casimir-Polder attraction; Atom clouds
Subjects:	Q Science > QC Physics > QC501 Electricity and magnetism
Faculties/Schools:	UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID:	57010
Depositing User:	Crawford, Rosemary
Date Deposited:	30 Mar 2020 08:36
Last Modified:	06 May 2020 09:18
URI:	https://eprints.nottingham.ac.uk/id/eprint/57010

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