98 research outputs found
A norm for Tsirelson's Banach space
We give an expression for the norm of the space constructed by Tsirelson. The
implicit equation satisfied by this norm is dual to the implicit equation for
the norm of the dual of Tsirelson space given by Figiel and Johnson. The
expression can be modified to give the norm of the dual of any mixed Tsirelson
space. In particular, our results can be adapted to give the norm for the dual
of Schlumprecht space
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
Tuning the proximity effect in a superconductor-graphene-superconductor junction
We have tuned in situ the proximity effect in a single graphene layer coupled
to two Pt/Ta superconducting electrodes. An annealing current through the
device changed the transmission coefficient of the electrode/graphene
interface, increasing the probability of multiple Andreev reflections. Repeated
annealing steps improved the contact sufficiently for a Josephson current to be
induced in graphene.Comment: Accepted for publication in Phys. Rev.
Towards spin injection from silicon into topological insulators: Schottky barrier between Si and Bi2Se3
A scheme is proposed to electrically measure the spin-momentum coupling in
the topological insulator surface state by injection of spin polarized
electrons from silicon. As a first approach, devices were fabricated consisting
of thin (<100nm) exfoliated crystals of Bi2Se3 on n-type silicon with
independent electrical contacts to silicon and Bi2Se3. Analysis of the
temperature dependence of thermionic emission in reverse bias indicates a
barrier height of 0.34 eV at the Si-Bi2Se3 interface. This robust Schottky
barrier opens the possibility of novel device designs based on sub-band gap
internal photoemission from Bi2Se3 into Si
Phonon assisted dynamical Coulomb blockade in a thin suspended graphite sheet
The differential conductance in a suspended few layered graphene sample is
fou nd to exhibit a series of quasi-periodic sharp dips as a function of bias
at l ow temperature. We show that they can be understood within a simple model
of dyn amical Coulomb blockade where energy exchanges take place between the
charge carriers transmitted trough the sample and a dissipative electromagnetic
envir onment with a resonant phonon mode strongly coupled to the electrons
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