130 research outputs found
Engineering a Spin-Orbit Bandgap in Graphene-Tellurium Heterostructures
Intensive research has focused on harnessing the potential of graphene for
electronic, optoelectronic, and spintronic devices by generating a bandgap at
the Dirac point and enhancing the spin-orbit interaction in the graphene layer.
Proximity to heavy p elements is a promising approach; however, their
interaction in graphene heterostructures has not been as intensively studied as
that of ferromagnetic, noble, or heavy d metals, neither as interlayers nor as
substrates. In this study, the effective intercalation of Te atoms in a
graphene on Ir(111) heterostructure is achieved. Combining techniques such as
low energy electron diffraction and scanning tunneling microscopy, the
structural evolution of the system as a function of the Te coverage is
elucidated, uncovering up to two distinct phases. The presented angle-resolved
photoemission spectroscopy analysis reveals the emergence of a bandgap of about
240 meV in the Dirac cone at room temperature, which preserves its
characteristic linear dispersion. Furthermore, a pronounced n-doping effect
induced by Te in the heterostructure is also observed, and remarkably the
possibility of tuning the Dirac point energy towards the Fermi level by
reducing the Te coverage while maintaining the open bandgap is demonstrated.
Spin-resolved measurements unveil a non-planar chiral spin texture with
significant splitting values for both in-plane and out-of-plane spin
components. These experimental findings are consistent with the development of
a quantum spin Hall phase, where a Te-enhanced intrinsic spin orbit coupling in
graphene surpasses the Rashba one and promotes the opening of the spin-orbit
bandgap.Comment: 9 pages, 4 figure
Engineering Periodic Dinuclear Lanthanide-Directed Networks Featuring Tunable Energy Level Alignment and Magnetic Anisotropy by Metal Exchange
Experimental Demonstration of a Magnetically Induced Warping Transition in a Topological Insulator Mediated by Rare-Earth Surface Dopants
2D Co-Directed MetalâOrganic Networks Featuring Strong Antiferromagnetism and Perpendicular Anisotropy
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger Observatory
The azimuthal asymmetry in the risetime of signals in Auger surface detector
stations is a source of information on shower development. The azimuthal
asymmetry is due to a combination of the longitudinal evolution of the shower
and geometrical effects related to the angles of incidence of the particles
into the detectors. The magnitude of the effect depends upon the zenith angle
and state of development of the shower and thus provides a novel observable,
, sensitive to the mass composition of cosmic rays
above eV. By comparing measurements with predictions from
shower simulations, we find for both of our adopted models of hadronic physics
(QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass
increases slowly with energy, as has been inferred from other studies. However,
the mass estimates are dependent on the shower model and on the range of
distance from the shower core selected. Thus the method has uncovered further
deficiencies in our understanding of shower modelling that must be resolved
before the mass composition can be inferred from .Comment: Replaced with published version. Added journal reference and DO
The Pierre Auger Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)
Contributions of the Pierre Auger Collaboration to the 34th International
Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The NetherlandsComment: 24 proceedings, the 34th International Cosmic Ray Conference, 30 July
- 6 August 2015, The Hague, The Netherlands; will appear in PoS(ICRC2015
Astrophysical Interpretation Of Pierre Auger Observatory Measurements Of The Uhecr Energy Spectrum And Mass Composition
13
- âŠ