10,530 research outputs found
Tribological Behavior of Very Thin Confined Films
The tribological properties of two smooth surfaces in the presence of a thin
confined film are investigated with a generic model for the interaction between
two surfaces and with computer simulations. It is shown that at large normal
contact pressures, an ultra thin film automatically leads to static friction
between two flat surfaces - even if the surfaces are incommensurate.
Commensurability is nevertheless the key quantity to understand the
tribological behavior of the contact. Qualitative differences between
commensurate and incommensurate contacts remain even in the presence of a thin
film. The differences mainly concern the thermal diffusion of the contact and
the transition between smooth sliding and stick-slip.Comment: 7 pages, 6 figure
Photoluminescence quenching in gold - MoS2 hybrid nanoflakes
Achieving tunability of two dimensional (2D) transition metal dichalcogenides
(TMDs) functions calls for the introduction of hybrid 2D materials by means of
localized interactions with zero dimensional (0D) materials. A
metal-semiconductor interface, as in gold (Au) - molybdenum disulfide (MoS2),
is of great interest from the standpoint of fundamental science as it
constitutes an outstanding platform to investigate plasmonic-exciton
interactions and charge transfer. The applied aspects of such systems introduce
new options for electronics, photovoltaics, detectors, gas sensing, catalysis,
and biosensing. Here we consider pristine MoS2 and study its interaction with
Au nanoislands, resulting in local variations of photoluminescence (PL)
associated with various Au-MoS2 hybrid configurations. By controllably
depositing monolayers of Au on MoS2 to form Au nanostructures of given size and
thickness, we investigate the electronic structure of the resulting hybrid
systems. We present strong evidence of PL quenching of MoS2 as a result of
charge transfer from MoS2 to Au: p-doping of MoS2. The results suggest new
avenues for 2D nanoelectronics, active control of transport or catalytic
properties
Pollution and the State: The Role of the Structure of Government
Government spending has significant environmental implications. This paper analyzes the effect of the allocation of government spending between public goods broadly defined and private goods or non-social subsidies on air and water pollution. The theoretical model predicts that a reallocation of expenditures from private subsidies to public goods improves environmental quality by reducing production pollution. We estimate an empirical model that shows that such a reallocation causes a significant reduction in air pollutants namely sulfur dioxide and lead and an improvement in water quality measures including dissolved oxygen and biological oxygen demand.
Zero-field spin splitting in a two-dimensional electron gas with the spin-orbit interaction revisited
We consider a two-dimensional electron gas (2DEG) with the Rashba spin-orbit
interaction (SOI) in presence of a perpendicular magnetic field. We derive
analytical expressions of the density of states (DOS) of a 2DEG with the Rashba
SOI in presence of magnetic field by using the Green's function technique. The
DOS allows us to obtain the analytical expressions of the magnetoconductivities
for spin-up and spin-down electrons. The conductivities for spin-up and
spin-down electrons oscillate with different frequencies and gives rise to the
beating patterns in the amplitude of the Shubnikov de Hass (SdH) oscillations.
We find a simple equation which determines the zero-field spin splitting energy
if the magnetic field corresponding to any beat node is known from the
experiment. Our analytical results reproduce well the experimentally observed
non-periodic beating patterns, number of oscillations between two successive
nodes and the measured zero-field spin splitting energy.Comment: 5 pages, 2 figure
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