Spinorial formulation of the 
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-BSE equations and spin properties of excitons in two-dimensional transition metal dichalcogenides

Marsili, Margherita; Molina-Sánchez, Alejandro; Palummo, Maurizia; Sangalli, Davide; Marini, Andrea

doi:10.1103/physrevb.103.155152

Cited by 25 publications

(14 citation statements)

References 78 publications

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“…A detailed description of the implementation and a comparison with other simplified approaches (like the perturbative SOC) can be found in Ref. [92]. Since the BSE is written in transition space, the definition of the excitonic matrix is not differ-ent from the collinear cases of both unpolarized and spincollinear systems.…”

Section: Spin-orbit Coupling and Kerrmentioning

confidence: 99%

Many-body perturbation theory calculations using the yambo code

Sangalli

Ferretti

Miranda

et al. 2019

J. Phys.: Condens. Matter

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380

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yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo's capabilities include the calculation of linear response quantities (both independentparticle and including electron-hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron-phonon interactions to the implementation of a real-time propagation scheme for simulating linear and nonlinear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools. CONTENTS

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Section: Spin-orbit Coupling and Kerrmentioning

confidence: 99%

Many-body perturbation theory calculations using the yambo code

Sangalli

Ferretti

Miranda

et al. 2019

J. Phys.: Condens. Matter

Self Cite

380

349

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“…We are also indebted to M. Palummo for sharing input files for the GW-BSE calculations of MoSe 2 based on Ref. [85] and for discussions about pseudopotentials.…”

Section: Acknowledgementsmentioning

confidence: 99%

“…DFT and DFPT. We used norm-conserving, fully relativistic pseudopotentials 99 and included spin-orbit interaction at all stages of the calculations, working with spinorial wafe functions 85 . Our 2D hexagonal systems have lattice parameter a = 5.90 (MoS 2 ) and a = 6.15 (MoSe 2 ) bohrs, with about 40 bohrs of vacuum separating repeated copies of the simulation supercells in the c direction.…”

Section: Appendix B: Mathematical Conventionsmentioning

confidence: 99%

“…For MoSe 2 we used instead the quasiparticle corrections previously calculated in Ref. [85] at the G 0 W 0 level, where the relevant details may be found. We computed the BSE both with (reducible, optical) and without (irreducible, elemental) the exchange contribution to the excitonic kernel, all in the Tamm-Dancoff approximation 101 (i.e., the kernel includes only resonant or antiresonant electron-hole transitions; this common approximation usually works well for gapped semiconductors and is a requirement for the excitonphonon treatment).…”

Section: Appendix B: Mathematical Conventionsmentioning

confidence: 99%

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Exciton-phonon interaction calls for a revision of the "exciton" concept

Paleari¹,

Marini²

2022

Preprint

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The concept of optical exciton -a photo-excited bound electron-hole pair within a crystal -is routinely used to interpret and model a wealth of excited-state phenomena in semiconductors. Beside originating sub-band gap signatures in optical spectra, optical excitons have also been predicted to condensate, diffuse, recombine, relax. However, all these phenomena are rooted on a theoretical definition of the excitonic state based on the following simple picture: "excitons" are actual particles that both appear as peaks in the linear absorption spectrum and also behave as well-defined quasiparticles. In this paper we show, instead, that the electron-phonon interaction decomposes the initial optical (i.e., "reducible") excitons into elemental (i.e., "irreducible") excitons, the latter being a different kind of bound electron-hole pairs lacking the effect caused by the induced, classical, electric field. This is demonstrated within a real-time, many-body perturbation theory approach starting from the interacting electronic Hamiltonian including both electron-phonon and electronhole interactions. We then apply the results on two realistic and paradigmatic systems, monolayer MoS2 (where the lowest-bound optical exciton is optically inactive) and monolayer MoSe2 (where it is optically active), using first-principles methods to compute the exciton-phonon coupling matrix elements. Among the consequences of optical-elemental decomposition, we point to a homogeneous broadening of absorption peaks occurring even for the lowest-bound optical exciton , and we provide a lower bound for the exciton linewidths. More generally, our findings suggest that the optical excitons gradually lose their initial structure and evolve as elemental excitons . These states can be regarded as the real intrinsic excitations of the interacting system, the ones that survive when the external perturbation and the induced electric fields have vanished.

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“…In this Letter, by combining time-resolved broadband optical reflectivity measurements with state-of-theart spinorial ab-initio-BSE calculations [22], we unveil the spectral fingerprints of exciton-phonon coupling in a representative van-der-Waals-layered semiconductor, the bismuth tri-iodide (BiI 3 ) single crystal. Recently, BiI 3 has come into focus as an efficient non-toxic replacement of lead-based perovskites in optoelectronic applications [23,24].…”

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confidence: 99%

Photoinduced coherent modulation of an excitonic resonance via coupling with coherent optical phonons

Mor,

Gosetti,

Molina-Sánchez

et al. 2021

Preprint

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The coupling of excitons with atomic vibrations plays a pivotal role on the nonequilibrium optical properties of layered semiconductors. However, addressing the dynamical interaction between excitons and phonons represents a hard task both experimentally and theoretically. By means of time-resolved broadband optical reflectivity combined with state-of-the-art ab-initio calculations of a bismuth triiodide single crystal, we unravel the universal spectral fingerprints of exciton-phonon coupling in layered semiconductors. Furthermore, we microscopically relate a photoinduced coherent energy modulation of the excitonic resonance to coherent optical phonons, thereby tracking the extent of the photoinduced atomic displacement in real-space. Our findings represent a step forward on the road to coherent manipulation of the excitonic properties on ultrafast timescales.

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Spinorial formulation of the GW -BSE equations and spin properties of excitons in two-dimensional transition metal dichalcogenides

Cited by 25 publications

References 78 publications

Many-body perturbation theory calculations using the yambo code

Many-body perturbation theory calculations using the yambo code

Exciton-phonon interaction calls for a revision of the "exciton" concept

Photoinduced coherent modulation of an excitonic resonance via coupling with coherent optical phonons

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