675 research outputs found
Crediting multi-authored papers to single authors
A fair assignment of credit for multi-authored publications is a
long-standing issue in scientometrics. In the calculation of the -index, for
instance, all co-authors receive equal credit for a given publication,
independent of a given author's contribution to the work or of the total number
of co-authors. Several attempts have been made to distribute the credit in a
more appropriate manner. In a recent paper, Hirsch has suggested a new way of
credit assignment that is fundamentally different from the previous ones: All
credit for a multi-author paper goes to a single author, the called
``-author'', defined as the person with the highest current -index
not the highest -index at the time of the paper's publication) (J. E.
Hirsch, Scientometrics 118, 673 (2019)). The collection of papers this author
has received credit for as -author is then used to calculate a new
index, , following the same recipe as for the usual index. The
objective of this new assignment is not a fairer distribution of credit, but
rather the determination of an altogether different property, the degree of a
person's scientific leadership. We show that given the complex time dependence
of for individual scientists, the approach of using the current value
instead of the historic one is problematic, and we argue that it would be
feasible to determine the -author at the time of the paper's
publication instead. On the other hand, there are other practical
considerations that make the calculation of the proposed very
difficult. As an alternative, we explore other ways of crediting papers to a
single author in order to test early career achievement or scientific
leadership.Comment: 6 pages, 4 figure
Extracting the Temperature of Hot Carriers in Time- and Angle-Resolved Photoemission
The interaction of light with a material's electronic system creates an
out-of-equilibrium (non-thermal) distribution of optically excited electrons.
Non-equilibrium dynamics relaxes this distribution on an ultrafast timescale to
a hot Fermi-Dirac distribution with a well-defined temperature. The advent of
time- and angle-resolved photoemission spectroscopy (TR-ARPES) experiments has
made it possible to track the decay of the temperature of the excited hot
electrons in selected states in the Brillouin zone, and to reveal their cooling
in unprecedented detail in a variety of emerging materials. It is, however, not
a straightforward task to determine the temperature with high accuracy. This is
mainly attributable to an a priori unknown position of the Fermi level and the
fact that the shape of the Fermi edge can be severely perturbed when the state
in question is crossing the Fermi energy. Here, we introduce a method that
circumvents these difficulties and accurately extracts both the temperature and
the position of the Fermi level for a hot carrier distribution by tracking the
occupation statistics of the carriers measured in a TR-ARPES experiment.Comment: 17 pages, 5 figure
Simultaneous quantization of bulk conduction and valence states through adsorption of nonmagnetic impurities on Bi2Se3
Exposing the (111) surface of the topological insulator Bi2Se3 to carbon
monoxide results in strong shifts of the features observed in angle-resolved
photoemission. The behavior is very similar to an often reported `aging' effect
of the surface and it is concluded that this aging is most likely due to the
adsorption of rest gas molecules. The spectral changes are also similar to
those recently reported in connection with the adsorption of the magnetic
adatom Fe. All spectral changes can be explained by a simultaneous confinement
of the conduction band and valence band states. This is only possible because
of the unusual bulk electronic structure of Bi2Se3. The valence band
quantization leads to spectral features which resemble those of a band gap
opening at the Dirac point.Comment: 5 pages, 4 figure
Detecting the local transport properties and the dimensionality of transport of epitaxial graphene by a multi-point probe approach
The electronic transport properties of epitaxial monolayer graphene (MLG) and
hydrogen-intercalated quasi free-standing bilayer graphene (QFBLG) on SiC(0001)
are investigated by micro multi-point probes. Using a probe with 12 contacts,
we perform four-point probe measurements with the possibility to effectively
vary the contact spacing over more than one order of magnitude, allowing us to
establish that the transport is purely two-dimensional. Combined with the
carrier density obtained by angle-resolved photoemission spectroscopy, we find
the room temperature mobility of MLG to be (870+-120)cm2/Vs. The transport in
QFBLG is also found to be two-dimensional with a mobility of (1600+-160)
cm2/Vs
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