title: Low temperature magneto-morphological characterisation of coronene and the resolution of previously observed unexplained phenomena.
abstract: The polyaromatic hydrocarbon coronene has been the molecule of choice for understanding the physical properties of graphene for over a decade. The modelling of the latter by the former was considered to be valid, as since it was first synthesised in 1932, the physical behaviour of coronene has been determined extremely accurately. We recently discovered however, an unforeseen polymorph of coronene, which exists as an enantiotrope with the previously observed crystal structure. Using low-temperature magnetisation and crystallographic measurements, we show here for the first time that the electronic and magnetic properties of coronene depend directly on the temperature at which it is observed, with hysteretic behaviour exhibited between 300 K and 100 K. Furthermore we determine that this behaviour is a direct result of the appearance and disappearance of the newly-discovered polymorph during thermal cycling. Our results not only highlight the need for theoretical models of graphene to take into account this anomalous behaviour at low temperatures, but also explain puzzling experimental observations of coronene dating back over 40 years.
authors.affiliation: Complex Functional Materials Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom.
authors.forename: Jason
authors.initials: J
authors.lastname: Potticary
authors.affiliation: Department of Materials Science and Engineering Sir Robert Hadfield Building, Mappin Street Sheffield S1 3JD, United Kingdom.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Boston
authors.affiliation: Department of Chemistry, Durham University, Lower Mountjoy, South Road, Durham, DH1 3LE, United Kingdom.|Department of Chemistry, University of Malta, Msida, MSD2080, Malta.
authors.forename: Liana
authors.initials: L
authors.lastname: Vella-Zarb
authors.affiliation: Complex Functional Materials Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom.
authors.forename: Alex
authors.initials: A
authors.lastname: Few
authors.affiliation: School of Physics, HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom.
authors.forename: Christopher
authors.initials: C
authors.lastname: Bell
authors.affiliation: Complex Functional Materials Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom.
authors.forename: Simon R
authors.initials: SR
authors.lastname: Hall