arXiv subjects

A. Stange

Publications and source records attributed to A. Stange.

7 recordsLinked to original sources

arXiv2019

Larger than 80$\,$% Valley Polarization of Free Carriers in Singly-Oriented Single Layer WS$_2$ on Au(111)

We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the K and K' points in singly-oriented single layer WS$_2$/Au(111). Our results reveal that in the valence band maximum an ultimate valley polarization of free holes of 84$\,$% can be achieved upon excitation with circularly polarized light at room temperature. Notably, we observe a significantly smaller valley polarization for the photoexcited free electrons in the conduction band minimum. Clear differences in the carrier dynamics between electrons and holes imply intervalley scattering processes into dark states being responsible for the efficient depolarization of the excited electron population.

cond-mat.mtrl-sci↗

arXiv2013

Ultrafast modulation of the chemical potential in BaFe$_2$As$_2$ by coherent phonons

Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe$_2$As$_2$ around the high-symmetry points $Γ$ and $M$. A global oscillation of the Fermi level at the frequency of the $A_{1g}$(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited surface region that arises from the high sensitivity of the band structure near the Fermi level to the $A_{1g}$ phonon mode combined with a low electron diffusivity perpendicular to the layers. The results establish a novel way to tune the electronic properties of iron pnictides: coherent control of the effective chemical potential. The results further suggest that the equilibration time for the effective chemical potential needs to be considered in the ultrafast electronic structure dynamics of materials with weak interlayer coupling.

cond-mat.supr-con↗

arXiv1996

Weakly-Coupled Higgs Bosons

We review the search for the standard Higgs boson, the Higgs bosons of the supersymmetric standard model, and Higgs bosons from a variety of other models at present and future colliders.

hep-ph↗

arXiv1994

Associated Production of Higgs and Weak Bosons, with H -> b\bar b, at Hadron Colliders

We consider the search for the Higgs boson at a high-luminosity Fermilab Tevatron, an upgraded Tevatron of energy 3.5 TeV, and the CERN Large Hadron Collider, via $WH/ZH$ production followed by H -> bb~ and leptonic decay of the weak vector bosons. We show that each of these colliders can potentially observe the standard Higgs boson in the intermediate-mass range, 80 GeV γγat the LHC. In addition, it can potentially be used to observe the lightest Higgs scalar of the minimal supersymmetric model in a region of parameter space not accessible to CERN LEP II or the LHC (using h -> γγ,ZZ^*).

hep-ph↗

arXiv1994

Higgs Decay to Top Quarks at Hadron Colliders

Higgs bosons which decay principally to top quarks, such as in the minimal supersymmetric model, produce a peak-dip structure in the $gg\to t\bar t$ invariant-mass spectrum. This structure is potentially observable at the CERN Large Hadron Collider. (see BNL theory home page http://penguin.phy.bnl.gov/bnl.html for recent preprints)

hep-ph↗

arXiv1993

Higgs Bosons at the Fermilab Tevatron

The Wjj background has increased by 70%. This decreases the significance of the WH signal somewhat. The significance of the ZH signal remains about the same.

hep-ph↗

arXiv1993

THE $t\bar tγ$ BACKGROUND TO $pp\rightarrow Wγ+ X$ AT THE SSC

We calculate the $pp\rightarrow t\bar tγ+X\rightarrow Wγ+ X$ cross section at SSC energies. Approximately 40\% of the total cross section originates from photon bremsstrahlung off the final state jet in $t\bar tj$ production. Without cuts restricting the hadronic activity, the $t\bar tγ$ rate is a factor 10 (2) larger than the tree level $Wγ$ cross section for a top quark mass of 110~GeV (200~GeV). Imposing a jet veto cut, the $t\bar tγ$ rate can be suppressed to a level well below the $Wγ+0$~jet signal cross section.

hep-ph↗