Excitons consist of electrons and holes held together by their attractive Coulomb interaction. Although excitons are neutral excitations, spatial fluctuations in their charge density couple with the ions of the crystal lattice. This coupling can lower the exciton energy and lead to the formation of a localized excitonic polaron or even a self-trapped exciton in the presence of strong exciton-phonon interactions. Here, we develop a theoretical and computational approach to compute excitonic polarons and self-trapped excitons from first principles. Our methodology combines the many-body Bethe-Salpeter approach with density-functional perturbation theory and does not require explicit supercell calculations. As a proof of concept, we demonstrate our method for a compound of the halide perovskite family.
Atom-ion hybrid systems are promising platforms for the quantum simulation of polaron physics in certain quantum materials. Here, we investigate the ionic Fermi polaron, a charged impurity in a polarized Fermi bath, at zero temperature using quantum Monte Carlo techniques. We compute the energy spectrum, residue, effective mass, and structural properties.
Lower-dimensional organic-inorganic hybrid perovskite materials promise to revolutionize the optoelectronics industry due to the tremendous possibilities of exotic control on excitonic properties driven via quantum confinement. Flexible organic cations acting as spacers and stabilizers enhance electron-phonon couplings, further amplifying the potential for modular light-matter interactions in these materials. Herein we unravel the nature of excitons in a quasi-1D chain of corner-sharing bismuth iodide octahedra with an intrinsic quantum well structure stabilized by a hexyl-diammonium cation.
Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials and Key Lab of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education; School of Resources, Environmental and Materials, Guangxi University, Nanning 530004, People's Republic of China.
Due to the easy transformation to the non-luminous yellow-CsPbIphase in air,-CsPbInanocrystalline materials with red light emission find limited applications. Lifting its structural stability is a challenge in its quantum dot (QD) lighting field. Here we studied the doping of Mnions (5.
We study a mechanism to induce superconductivity in atomically thin semiconductors where excitons mediate an effective attraction between electrons. Our model includes interaction effects beyond the paradigm of phonon-mediated superconductivity and connects to the well-established limits of Bose and Fermi polarons. By accounting for the strong-coupling physics of trions, we find that the effective electron-exciton interaction develops a strong frequency and momentum dependence accompanied by the system undergoing an emerging BCS-BEC crossover from weakly bound s-wave Cooper pairs to a superfluid of bipolarons.
The formation of excited dimer states, so called excimers, is an important phenomenon in many organic molecular semiconductor solid state aggregates. In contrast to Frenkel exciton-polarons, an excimer is long-lived and energetically low-lying due to stabilization resulting from a substantial reorganization of the intermolecular geometry. Here, we show that ultrafast electron diffraction can follow the dynamics of solid-state excimer formation in polycrystalline thin films of a molecular semiconductor, revealing both the key reaction modes and the eventual structure of the emitting state.
