10 research outputs found
Orbital character effects in the photon energy and polarization dependence of pure C60 photoemission
Recent direct experimental observation of multiple highly-dispersive C
valence bands has allowed for a detailed analysis of the unique photoemission
traits of these features through photon energy- and polarization-dependent
measurements. Previously obscured dispersions and strong photoemission traits
are now revealed by specific light polarizations. The observed intensity
effects prove the locking in place of the C molecules at low
temperatures and the existence of an orientational order imposed by the
substrate chosen. Most importantly, photon energy- and polarization-dependent
effects are shown to be intimately linked with the orbital character of the
C band manifolds which allows for a more precise determination of the
orbital character within the HOMO-2. Our observations and analysis provide
important considerations for the connection between molecular and crystalline
C electronic structure, past and future band structure studies, and for
increasingly popular C electronic device applications, especially those
making use of heterostructures
Linearly dispersive bands at the onset of correlations in KC films
Molecular crystals are a flexible platform to induce novel electronic phases.
Due to the weak forces between molecules, intermolecular distances can be
varied over relatively larger ranges than interatomic distances in atomic
crystals. On the other hand, the hopping terms are generally small, which
results in narrow bands, strong correlations and heavy electrons. Here, by
growing KC fullerides on hexagonal layered BiSe, we show
that upon doping the series undergoes a Mott transition from a molecular
insulator to a correlated metal, and an in-gap state evolves into highly
dispersive Dirac-like fermions at half filling, where superconductivity occurs.
This picture challenges the commonly accepted description of the low energy
quasiparticles as appearing from a gradual electron doping of the conduction
states, and suggests an intriguing parallel with the more famous family of the
cuprate superconductors. More in general, it indicates that molecular crystals
offer a viable route to engineer electron-electron interactions.Comment: 5 pages, 4 figures. Accepted at Physical Review Researc
Recommended from our members
Orbital Character Effects in the Photon Energy and Polarization Dependence of Pure C60 Photoemission.
Recent direct experimental observation of multiple highly dispersive C60 valence bands has allowed for a detailed analysis of the unusual photoemission traits of these features through photon energy- and polarization-dependent measurements. Previously obscured dispersions and strong photoemission traits are now revealed by specific light polarizations. The observed intensity effects prove the locking in place of the C60 molecules at low temperatures and the existence of an orientational order imposed by the substrate chosen. Most importantly, photon energy- and polarization-dependent effects are shown to be intimately linked with the orbital character of the C60 band manifolds which allow for a more precise determination of the orbital character within the third highest occupied molecular orbital (HOMO-2). Our observations and analysis provide important considerations for the connection between molecular and crystalline C60 electronic structure, past and future band structure studies, and for increasingly popular C60 electronic device applications, especially those making use of heterostructures
Recommended from our members
Polarization dependent photoemission as a probe of the magnetic ground state in the van der Waals ferromagnet VI3
Van der Waals ferromagnets are thrilling materials from both a fundamental and technological point of view. VI3 is an interesting example, with a complex magnetism that differentiates it from the first reported Cr based layered ferromagnets. Here, we show in an indirect way through angle resolved photoemission spectroscopy experiments, the importance of spin-orbit coupling setting the electronic properties of this material. Our light polarized photoemission measurements point to a ground state with a half-filled e ± ′ doublet, where a gap opening is triggered by spin-orbit coupling enhanced by electronic correlations
Molecular Arrangement and Charge Transfer in C<sub>60</sub>/Graphene Heterostructures
Charge
transfer at the interface between dissimilar materials is
at the heart of electronics and photovoltaics. Here we study the molecular
orientation, electronic structure, and local charge transfer at the
interface region of C<sub>60</sub> deposited on graphene, with and
without supporting substrates such as hexagonal boron nitride. We
employ <i>ab initio</i> density functional theory with van
der Waals interactions and experimentally characterize interface devices
using high-resolution transmission electron microscopy and electronic
transport. Charge transfer between C<sub>60</sub> and the graphene
is found to be sensitive to the nature of the underlying supporting
substrate and to the crystallinity and local orientation of the C<sub>60</sub>. Even at room temperature, C<sub>60</sub> molecules interfaced
to graphene are orientationally locked into position. High electron
and hole mobilities are preserved in graphene with crystalline C<sub>60</sub> overlayers, which has ramifications for organic high-mobility
field-effect devices