5,781 research outputs found
Anisotropic exciton Stark shift in black phosphorus
We calculate the excitonic spectrum of few-layer black phosphorus by direct
diagonalization of the effective mass Hamiltonian in the presence of an applied
in-plane electric field. The strong attractive interaction between electrons
and holes in this system allows one to investigate the Stark effect up to very
high ionizing fields, including also the excited states. Our results show that
the band anisotropy in black phosphorus becomes evident in the direction
dependent field induced polarizability of the exciton
Topological confinement in graphene bilayer quantum rings
We demonstrate the existence of localized electron and hole states in a
ring-shaped potential kink in biased bilayer graphene. Within the continuum
description, we show that for sharp potential steps the Dirac equation
describing carrier states close to the K (or K') point of the first Brillouin
zone can be solved analytically for a circular kink/anti-kink dot. The
solutions exhibit interfacial states which exhibit Aharonov-Bohm oscillations
as functions of the height of the potential step and/or the radius of the ring
Magentically-Induced Lattice Distortions and Ferroelectricity in Magnetoelectric GdMnO3
In this work we investigate the magnetic field dependence of Ag octahedra
rotation (tilt) and B2g symmetric stretching modes frequency at different
temperatures. Our field-dependent Raman investigation at 10K is interpreted by
an ionic displacive nature of the magnetically induced ferroelectric phase
transition. The frequency change of the Ag tilt is in agreement with the
stabilization of the Mn-Gd spin arrangement, yielding the necessary conditions
for the onset of ferroelectricity on the basis of the inverse
Dzyaloshinskii-Moriya interaction. The role of the Jahn-Teller cooperative
interaction is also evidenced by the change of the B2g mode frequency at the
ferroelectric phase transition. This frequency change allows estimating the
shift of the oxygen position at the ferroelectric phase transition and the
corresponding spontaneous polarization of 480 {\mu}C/m2, which agrees with
earlier reported values in single crystals. Our study also confirms the
existence of a large magnetic hysteresis at the lowest temperatures, which is a
manifestation of magnetrostiction.Comment: 5 pages, 3 figure
Late extensional shear zones and associated recumbent folds in the Alpujarride subduction complex, Betic Cordillera, southern Spain
The existence in the Alpujarride Complex (Betic Cordillera, southern Spain) of a relatively continuous extensional event (following crustal thickening) is based on detailed structural studies and is consistent with the P-T paths and geochronological data established for the Alpujarride rocks. According to our research, the Alpujarride Complex contains two large-scale shear zones accommodating early Miocene extension. The shear zones contain km-scale recumbent folds, some with sheath fold geometry, and megaboudinage structures, and are closely associated with detachment faults.Large-scale folds and boudins cause dome-like undulations in the detachments, which are inferred to overlap in time with the deformation in the shear zones. One shear zone in the eastern part of the orogen is top-N; the other, in the western part, is top-E. The change in the shear direction may represent a temporal evolution in the direction of shear, possibly related to a change in the subduction direction in space and time
Influência do peso de rizomas-semente na produção de açafrão.
O objetivo deste trabalho foi avaliar o efeito sobre a produção, do uso da classificação por peso dos rizomas-semente, de três acessos de açafrão, nas condições de Manaus, AM
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