14,536 research outputs found
Light charged Higgs boson production at the Large Hadron electron Collider
We study the production of a light charged Higgs boson at the future Large
Hadron electron Collider (LHeC), through the process
considering both decay channels and in the final state. We analyse these processes in the context of the
2-Higgs Doublet Model Type III (2HDM-III) and assess the LHeC sensitivity to
such signals against a variety of both reducible and irreducible
backgrounds. We confirm that prospects for detection in the 2HDM-III are
excellent assuming standard collider energy and luminosity conditions.Comment: 12 pages, 12 figures. Accepted in Physical Review
Suppression of electron scattering resonances in graphene by quantum dots
Transmission of low-energetic electrons through two-dimensional materials
leads to unique scattering resonances. These resonances contribute to
photoemission from occupied bands where they appear as strongly dispersive
features of suppressed photoelectron intensity. Using angle-resolved
photoemission we have systematically studied scattering resonances in epitaxial
graphene grown on the chemically differing substrates Ir(111), Bi/Ir, Ni(111)
as well as in graphene/Ir(111) nanopatterned with a superlattice of uniform Ir
quantum dots. While the strength of the chemical interaction with the substrate
has almost no effect on the dispersion of the scattering resonances, their
energy can be controlled by the magnitude of charge transfer from/to graphene.
At the same time, a superlattice of small quantum dots deposited on graphene
eliminates the resonances completely. We ascribe this effect to a
nanodot-induced buckling of graphene and its local rehybridization from
sp to sp towards a three-dimensional structure. Our results suggest
nanopatterning as a prospective tool for tuning optoelectronic properties of
two-dimensional materials with graphene-like structure.Comment: The following article has been submitted to Applied Physics Letters.
If it is published, it will be found online at http://apl.aip.or
Rashba splitting of 100 meV in Au-intercalated graphene on SiC
Intercalation of Au can produce giant Rashba-type spin-orbit splittings in
graphene but this has not yet been achieved on a semiconductor substrate. For
graphene/SiC(0001), Au intercalation yields two phases with different doping.
Here, we report the preparation of an almost pure p-type graphene phase after
Au intercalation. We observe a 100 meV Rashba-type spin-orbit splitting at 0.9
eV binding energy. We show that this giant splitting is due to hybridization
and much more limited in energy and momentum space than for Au-intercalated
graphene on Ni
Laser-induced persistent photovoltage on the surface of a ternary topological insulator at room temperature
Using time- and angle-resolved photoemission, we investigate the ultrafast
response of excited electrons in the ternary topological insulator (BiSb)Te to fs-infrared pulses. We demonstrate that at the
critical concentration =0.55, where the system becomes bulk insulating, a
surface voltage can be driven at room temperature through the topological
surface state solely by optical means. We further show that such a photovoltage
persists over a time scale that exceeds 6 s, i.e, much longer than
the characteristic relaxation times of bulk states. We attribute the origin of
the photovoltage to a laser-induced band-bending effect which emerges near the
surface region on ultrafast time scales. The photovoltage is also accompanied
by a remarkable increase in the relaxation times of excited states as compared
to undoped topological insulators. Our findings are relevant in the context of
applications of topological surface states in future optical devices.Comment: 5 pages, 4 figure
Ultrafast spin polarization control of Dirac fermions in topological insulators
Three-dimensional topological insulators (TIs) are characterized by
spin-polarized Dirac-cone surface states that are protected from backscattering
by time-reversal symmetry. Control of the spin polarization of topological
surface states (TSSs) using femtosecond light pulses opens novel perspectives
for the generation and manipulation of dissipationless surface spin currents on
ultrafast timescales. Using time-, spin-, and angle-resolved spectroscopy, we
directly monitor for the first time the ultrafast response of the spin
polarization of photoexcited TSSs to circularly-polarized femtosecond pulses of
infrared light. We achieve all-optical switching of the transient out-of-plane
spin polarization, which relaxes in about 1.2 ps. Our observations establish
the feasibility of ultrafast optical control of spin-polarized Dirac fermions
in TIs and pave the way for novel optospintronic applications at ultimate
speeds.Comment: 9 pages, 4 figure
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