121 research outputs found
A spin- and angle-resolving photoelectron spectrometer
A new type of hemispherical electron energy analyzer that permits angle and
spin resolved photoelectron spectroscopy has been developed. The analyzer
permits standard angle resolved spectra to be recorded with a two-dimensional
detector in parallel with spin detection using a mini-Mott polarimeter. General
design considerations as well as technical solutions are discussed and test
results from the Au(111) surface state are presented
Mn induced modifications of Ga 3d photoemission from (Ga, Mn)As: evidence for long range effects
Using synchrotron based photoemission, we have investigated the Mn-induced
changes in Ga 3d core level spectra from as-grown . Although Mn is located in Ga substitutional sites, and does
therefore not have any Ga nearest neighbours, the impact of Mn on the Ga core
level spectra is pronounced even at Mn concentrations in the range of 0.5%. The
analysis shows that each Mn atom affects a volume corresponding to a sphere
with around 1.4 nm diameter.Comment: Submitted to Physical Review B, Brief Repor
Photoemission evidence for crossover from Peierls-like to Mott-like transition in highly strained VO
We present a spectroscopic study that reveals that the metal-insulator
transition of strained VO thin films may be driven towards a purely
electronic transition, which does not rely on the Peierls dimerization, by the
application of mechanical strain. Comparison with a moderately strained system,
which does involve the lattice, demonstrates the crossover from Peierls- to
Mott-like transitions
Observation of Quantum-Tunneling Modulated Spin Texture in Ultrathin Topological Insulator Bi2Se3 Films
Understanding the spin-texture behavior of boundary modes in ultrathin
topological insulator films is critically essential for the design and
fabrication of functional nano-devices. Here by using spin-resolved
photoemission spectroscopy with p-polarized light in topological insulator
Bi2Se3 thin films, we report tunneling-dependent evolution of spin
configuration in topological insulator thin films across the metal-to-insulator
transition. We observe strongly binding energy- and wavevector-dependent spin
polarization for the topological surface electrons in the ultra-thin
gapped-Dirac-cone limit. The polarization decreases significantly with enhanced
tunneling realized systematically in thin insulating films, whereas magnitude
of the polarization saturates to the bulk limit faster at larger wavevectors in
thicker metallic films. We present a theoretical model which captures this
delicate relationship between quantum tunneling and Fermi surface spin
polarization. Our high-resolution spin-based spectroscopic results suggest that
the polarization current can be tuned to zero in thin insulating films forming
the basis for a future spin-switch nano-device.Comment: To appear in Nature Communications (2014); Expanded version of
http://arxiv.org/abs/1307.548
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