Predictions of moiré excitons in twisted two-dimensional organic–inorganic halide perovskites

Recent breakthrough in synthesizing arbitrary vertical heterostructures of Ruddlesden–Popper (RP) perovskites opens doors to myriad quantum optoelectronic applications. However, it is not clear whether moiré excitons and flat bands can be formed in such heterostructures. Here, we predict from first principles that twisted homobilayers of RP perovskite, MA₂PbI₄, can host moiré excitons and yield flat energy bands. The moiré excitons exhibit unique and hybridized characteristics with electrons confined in a single layer of a striped distribution while holes localized in both layers. Nearly flat valence bands can be formed in the bilayers with relatively large twist angles, thanks to the presence of hydrogen bonds that strengthen the interlayer coupling. External pressures can further increase the interlayer coupling, yielding more localized moiré excitons and flatter valence bands. Finally, electrostatic gating is predicted to tune the degree of hybridization, energy, position and localization of moiré excitons in twisted MA₂PbI₄ bilayers.

Excitonic states in twisted MA₂PbI₄ bilayers were calculated by first-principles calculations.     

Novel routes to 1-aryl-1,4-dihydro-3(2H)-isoquinolinones and 2-substituted or 2,3-disubstituted benzofurans by intramolecular cyclizations

N-(α-Benzotriazolylalkyl)arylacetamides, readily available from an arylacetamide, an aldehyde and benzotriazole, undergo intramolecular cyclization under acidic conditions to give 1-aryl-1,4-dihydro-3(2H)-isoquinolinones in good to excellent yields. Similarly, 2-(benzotriazol-1-yl)-2-(o-hydroxyphenyl)ethanols, obtained by lithiation of 2-(benzotriazol-1-ylmethyl)phenols followed by quenching with aldehydes or ketones, eliminate a molecule of water and a molecule of benzotriazole yielding 2-substituted and 2,3-disubstituted benzofurans.     

On the Riemann–Hilbert problem of the matrix Lakshmanan–Porsezian–Daniel system with a $$4\times4$$ AKNS-type matrix Lax pair

Theoretical and Mathematical Physics - The initial-boundary value problems for the matrix Lakshmanan–Porsezian–Daniel system are studied by utilizing the Fokas unified transform...     

On a Damped Vibration Problem Involving p-Laplacian Operator: Fast Homoclinic Orbits

In this paper, we deal with the nonlinear second-order differential equation with damped vibration term involving p-Laplacian operator. Of particular interest is the resolution of an open problem. An interesting outcome from our result is that we can obtain the fast homoclinic solution with general superlinear growth assumption in suitable Sobolev space. To our knowledge, our theorems appear to be the first such result about damped vibration problem with p-Laplacian operator.     

Sufficient Maximum Principle for Stochastic Optimal Control Problems with General Delays

Journal of Optimization Theory and Applications - This paper is to establish a sufficient maximum principle for one kind of stochastic optimal control problem with three types of delays: a discrete...     

Global well-posedness for the 3-D MHD equations with partial diffusion in the periodic domain

In this paper, we prove the global well-posedness of the 3-D magnetohydrodynamics(MHD) equations with partial diffusion in the periodic domain when the initial velocity is small and the initial magnetic field is close to a background magnetic field satisfying the Diophantine condition.     

Observation of isomeric states in197Bi

The high spin states of¹¹⁹Te, populated in¹¹⁰Pd(¹³C,4n) and¹¹⁰Pd(¹²C,3n) reactions, have been studied through -ray spectroscopy. The level scheme has been established upto a spin of 55/2. Three-quasiparticle states, based on g² _7/2h_11/2 and g_7/2d_5/2h_11/2 configurations, have been identified. The 35/2 and 39/2 states are suggested to be the fully aligned states constituted by five valence h_11/2 ³, g_7/2, d_5/2 quasiparticles.