187 research outputs found
Rich many-body phase diagram of electrons and holes in doped monolayer transition metal dichalcogenides
We use a variational technique to study the many-body phase diagram of
electrons and holes in -doped and -doped monolayer transition metal
dichalcogenides (TMDs). We find a total of four different phases. ) A fully
spin polarized and valley polarized ferromagnetic state. ) A state with no
global spin polarization but with spin polarization in each valley separately,
i.e. spin-valley locking. ) A state with spin polarization in one of the
valleys and little to no spin polarization in the other valley. ) A
paramagnetic state with no valley polarization. These phases are separated by
first-order phase transitions and are determined by the particle density and
the dielectric constant of the substrate. We find that in the presence of a
perpendicular magnetic field the four different phases persist. In the case of
-doped MoS, a fifth phase, which is completely valley polarized but not
spin polarized, appears for magnetic fields larger than 7 T and for magnetic
fields larger than 23 T completely replaces the second phase.Comment: 8 pages, 4 figures, 1 tabl
Excitonic complexes in anisotropic atomically thin two-dimensional materials: black phosphorus and TiS
The effect of anisotropy in the energy spectrum on the binding energy and
structural properties of excitons, trions, and biexcitons is investigated. To
this end we employ the stochastic variational method with a correlated Gaussian
basis. We present results for the binding energy of different excitonic
complexes in black phosphorus (bP) and TiS and compare them with recent
results in the literature when available, for which we find good agreement. The
binding energies of excitonic complexes in bP are larger than those in TiS.
We calculate the different average interparticle distances in bP and TiS
and show that excitonic complexes in bP are strongly anisotropic whereas in
TiS they are almost isotropic, even though the constituent particles have
an anisotropic energy spectrum. This is also confirmed by the correlation
functions.Comment: 6 pages, 4 figures, 3 table
Comment on "Creating in-plane pseudomagnetic fields in excess of 1000 T by misoriented stacking in a graphene bilayer"
In a recent paper [Phys. Rev. B 89, 125418 (2014)], the authors argue that it
is possible to map the electronic properties of twisted bilayer graphene to
those of bilayer graphene in an in-plane magnetic field. However, their
description of the low-energy dynamics of twisted bilayer graphene is
restricted to the extended zone scheme and therefore neglects the effects of
the superperiodic structure. If the energy spectrum is studied in the supercell
Brillouin zone, we find that the comparison with an in-plane magnetic field
fails because (i) the energy spectra of the two situations exhibit different
symmetries and (ii) the low-energy spectra are very different.Comment: 3 pages, 2 figure
Excitons and trions in monolayer transition metal dichalcogenides: A comparative study between the multiband model and the quadratic single-band model
The electronic and structural properties of excitons and trions in monolayer
transition metal dichalcogenides are investigated using both a multiband and a
single-band model. In the multiband model we construct the excitonic
Hamiltonian in the product base of the single-particle states at the conduction
and valence band edges. We decouple the corresponding energy eigenvalue
equation and solve the resulting differential equation self-consistently, using
the finite element method (FEM), to determine the energy eigenvalues and the
wave functions. As a comparison, we also consider the simple single-band model
which is often used in numerical studies. We solve the energy eigenvalue
equation using the FEM as well as with the stochastic variational method (SVM)
in which a variational wave function is expanded in a basis of a large number
of correlated Gaussians. We find good agreement between the results of both
methods, as well as with other theoretical works for excitons, and we also
compare with available experimental data. For trions the agreement between both
methods is not as good due to our neglect of angular correlations when using
the FEM. Finally, when comparing the two models, we see that the presence of
the valence bands in the mutiband model leads to differences with the
single-band model when (interband) interactions are strong.Comment: 14 pages, 11 figures, 3 table
Coacervation in aqueous solutions of short chain tetraalkylammonium bromide and sodium silicate
Coacervation (liq./liq. sepn.) takes place in aq. solns. contg. short chain tetraalkylammonium (TAA) and silicate ions when other ions (Na+, Br-) are present. The TAA bromide is predominantly present in the upper layer and the Na silicate is mainly present in the lower layer. The coacervation can be described using the activity coeffs. of the 2 sep. salts and a Redlich-Kister type excess Gibbs free energy. Since part of the Gibbs free energy is dependent on the enthalpy of hydrophobic hydration of the TAA ions, the driving force for coacervation is ascribed to a mismatch of the hydration layers around the silicate and TAA ions. [on SciFinder (R)
Description of the New Netherlands
Originally published as Beschryvinge van Nieuvv-Nederlant in 1655, this edition is a translation from the original Dutch by Jeremiah Johnson. It is part of the series Old South leaflets [General series., v. 4, no. 69].https://digitalcommons.cedarville.edu/pamphlet_collection/1053/thumbnail.jp
A doping-dependent switch from one- to two-component superfluidity at temperature above 100K in coupled electron-hole Van der Waals heterostructures
The hunt for high temperature superfluidity has received new impetus from the
discovery of atomically thin stable materials. Electron-hole superfluidity in
coupled MoSe2-WSe2 monolayers is investigated using a mean-field multiband
model that includes the band splitting caused by the strong spin-orbit
coupling. The splitting leads to a large energy misalignment of the electron
and hole bands which can be markedly changed by interchanging the doping of the
monolayers. The choice of doping determines if the superfluidity is tuneable
from one- to two-components. The electron-hole pairing is strong, with high
transition temperatures in excess of 100 K
Do my emotions show or not? Problems with transparency estimation in women with borderline personality disorder features
Transparency estimation, that is, estimating the extent to which one’s mental states are observable to others, requires the simultaneous representation of the self and of others’ perspective on the self. Individuals with borderline personality disorder (BPD) have difficulty integrating multiple perspectives when mentalizing, which may be reflected in impaired transparency estimation. A total of 62 participants high and low in BPD features watched emotionally evocative video clips and estimated the transparency of their emotional experience while facial expression coding software (FaceReader) quantified their objective transparency. Individuals high in BPD features showed a larger discrepancy between estimated and objective transparency than individuals low in BPD features, showing that they both over- and underestimated their transparency. Indeed, estimated transparency positively predicted objective transparency in individuals low in BPD features, but not in individuals high in BPD features. Moreover, the ability to estimate intraindividual variability in one’s own objective transparency was moderated by self-reported arousal in the participants high in BPD features. Impairments in transparency estimation were correlated with self-report measures of borderline features, attachment, and mentalizing. In conclusion, we found that borderline features relate to a reduced capacity to estimate the extent to which one’s own emotional states are observable to others. Although replication in clinical samples of BPD patients is needed, the present study provides evidence for problems in mentalizing the (embodied) self from another person’s perspective in BPD
Sondeo arqueológico Cueva Pintada, detalle carbón [Material gráfico]
Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
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