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 $n$-doped and $p$-doped monolayer transition metal dichalcogenides (TMDs). We find a total of four different phases. $i$) A fully spin polarized and valley polarized ferromagnetic state. $ii$) A state with no global spin polarization but with spin polarization in each valley separately, i.e. spin-valley locking. $iii$) A state with spin polarization in one of the valleys and little to no spin polarization in the other valley. $iv$) 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 $n$-doped MoS$_2$, 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 TiS3_3

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$_3$ 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$_3$. We calculate the different average interparticle distances in bP and TiS$_3$ and show that excitonic complexes in bP are strongly anisotropic whereas in TiS$_3$ 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

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

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

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)

Catalyse supportée sur nanotubes de carbone

This PhD thesis deals with the catalysis supported on carbon nanotubes. Several aspects have been studied such as electrocatalysis for hydrogen production form water, catalysis for organic synthesis and electrocatalysis of the oxygen reduction reaction. Many different catalysts have been synthesized based on supramolecular assembly of amphiphilic molecules around carbon nanotubes or assembly of polyaromatic molecules at the surface of the nanotubes. These catalysts are made of metallic complexes or metallic nanoparticles. These catalysts have been successfully used to perform the reactions mentioned above.Cette thèse porte sur la catalyse supportée sur nanotubes de carbone. Plusieurs aspects ont été étudiés, électrocatalyse pour la production d'hydrogène à partir d'eau, catalyse pour la synthèse organique et électrocatalyse de la réaction de réduction de l'oxygène. Différents catalyseurs ont été synthétisés à partir d'assemblages supramoléculaires de molécules amphiphiles autour de nanotubes de carbone ou d'adhésion de molécules polyaromatiques à la surface des nanotubes et ont impliqué l'utilisation de catalyseur moléculaire ou nanoparticulaire. L'utilisation de ces catalyseurs pour les différents types de réactions mentionnés plus haut ont abouti à des résultats intéressants

Structural interpretation of the amino acid sequence of a second domain from the Artemia covalent polymer globin

Artemia has a complex extracellular hemoglobin of Mr 260,000 comprising two globin chains (Mr 130,000) each of which is a polymer of eight covalently linked domains of Mr 16,000. The primary structure of this polymeric globin was studied to understand how globin folded domains are ordered within a globin chain and, in turn, how the latter associate into a functional hemoglobin molecule. Here we report the amino acid sequence of a second domain, E7 (Mr 16,081, excluding the heme), and interpretations of sequence data by computer-assisted alignment and modeling. This clearly shows that, as with domain E1 (Moens, L. Van Hauwaert, M.-L. De Smet, K. Geelen, D. Verpooten, G. Van Beeumen, J. Wodak, S. Alard, P. & Trotman, C. (1988) J. Biol. Chem. 263, 4679-4685), domain E7 is compatible with a globin folded structure of the β-type chain. Several specific differences of domains E7 and E1 from the classic globins are identified. They possibly can be interpreted in terms of specific requirements for a double octameric functional molecule.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

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

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