2024
Marini, Andrea
Nonadiabatic effects lead to the breakdown of the semiclassical phonon picture Journal Article
In: Physical Review B, vol. 110, iss. 2, pp. 024306, 2024, ISSN: 2469-9969 (online), 2469-9950 (print).
Abstract | Links | BibTeX | Tags: Nanotechnology, Physics
@article{nokey,
title = {Nonadiabatic effects lead to the breakdown of the semiclassical phonon picture},
author = {Marini, Andrea},
editor = {American Physical Society},
url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.024306},
doi = {https://doi.org/10.1103/PhysRevB.110.024306},
issn = {2469-9969 (online), 2469-9950 (print)},
year = {2024},
date = {2024-07-03},
urldate = {2024-07-03},
journal = {Physical Review B},
volume = {110},
issue = {2},
pages = {024306},
abstract = {Phonon properties of realistic materials are routinely calculated within the density functional perturbation theory (DFPT). This is a semiclassical approach where the atoms are assumed to oscillate along classical trajectories immersed in the electronic Kohn–Sham system. In this paper, we demonstrate that, in metals, nonadiabatic effects induce a deviation of the DFTP phonon frequencies from the quantistic solution of the Dyson equation—a deviation that increases with the phonon energy width, reflecting the breakdown of the semiclassical DFPT description. The final message is that nonadiabatic phonon effects can be described only by using a fully quantistic approach.},
keywords = {Nanotechnology, Physics},
pubstate = {published},
tppubtype = {article}
}
Phonon properties of realistic materials are routinely calculated within the density functional perturbation theory (DFPT). This is a semiclassical approach where the atoms are assumed to oscillate along classical trajectories immersed in the electronic Kohn–Sham system. In this paper, we demonstrate that, in metals, nonadiabatic effects induce a deviation of the DFTP phonon frequencies from the quantistic solution of the Dyson equation—a deviation that increases with the phonon energy width, reflecting the breakdown of the semiclassical DFPT description. The final message is that nonadiabatic phonon effects can be described only by using a fully quantistic approach.
2022
CEP (Villegas Villegas, Cesar E. P. ) ; Leite
Efficient hot-carrier dynamics in near-infrared photocatalytic metals Journal Article
In: Physical Review B, vol. 105, iss. 16, no. 165109, 2022, ISSN: 2469-9950; eISSN 2469-9969.
Abstract | Links | BibTeX | Tags: Applied, Atomic and Molecular Physics, Condensed matter, General Materials Science, General Physics and Astronomy, Multidisciplinary, Physics
@article{nokey,
title = {Efficient hot-carrier dynamics in near-infrared photocatalytic metals},
author = {Villegas, CEP (Villegas, Cesar E. P.) ; Leite, MS (Leite, Marina S.) ; Marini, A (Marini, Andrea) ; Rocha, AR (Rocha, Alexandre R.)},
editor = {AMER PHYSICAL SOC},
url = {https://www.webofscience.com/wos/woscc/full-record/WOS:000807392800005},
doi = {10.1103/PhysRevB.105.165109},
issn = {2469-9950; eISSN 2469-9969},
year = {2022},
date = {2022-04-07},
journal = {Physical Review B},
volume = {105},
number = {165109},
issue = {16},
abstract = {Photoexcited metals can produce highly energetic hot carriers whose controlled generation and extraction is a promising avenue for technological applications. While hot-carrier dynamics in Au-group metals have been widely investigated, a microscopic description of the dynamics of photoexcited carriers in the mid-infrared and near-infrared Pt-group metals range is still scarce. Since these materials are widely used in catalysis and, more recently, in plasmonic catalysis, their microscopic carrier dynamics characterization is crucial. We employ ab initio many-body perturbation theory to investigate the hot-carrier generation, relaxation times, and mean free path in bulk Pd and Pt. We show that the direct optical transitions of photoexcited carriers in these metals are mainly generated in the near-infrared range. We also find that the electron-phonon mass enhancement parameter for Pt is 16% higher than Pd, a result that helps explain several experimental results showing diverse trends. Moreover, we predict that Pd (Pt) hot electrons possess total relaxation times of up to 35 fs (24 fs), taking place at approximately 0.5 eV (1.0 eV) above the Fermi energy. Finally, an efficient hot electron generation and extraction can be achieved in nanofilms of Pd (110) and Pd (100) when subject to excitation energies ranging from 0.4 to 1.6 eV.},
keywords = {Applied, Atomic and Molecular Physics, Condensed matter, General Materials Science, General Physics and Astronomy, Multidisciplinary, Physics},
pubstate = {published},
tppubtype = {article}
}
Photoexcited metals can produce highly energetic hot carriers whose controlled generation and extraction is a promising avenue for technological applications. While hot-carrier dynamics in Au-group metals have been widely investigated, a microscopic description of the dynamics of photoexcited carriers in the mid-infrared and near-infrared Pt-group metals range is still scarce. Since these materials are widely used in catalysis and, more recently, in plasmonic catalysis, their microscopic carrier dynamics characterization is crucial. We employ ab initio many-body perturbation theory to investigate the hot-carrier generation, relaxation times, and mean free path in bulk Pd and Pt. We show that the direct optical transitions of photoexcited carriers in these metals are mainly generated in the near-infrared range. We also find that the electron-phonon mass enhancement parameter for Pt is 16% higher than Pd, a result that helps explain several experimental results showing diverse trends. Moreover, we predict that Pd (Pt) hot electrons possess total relaxation times of up to 35 fs (24 fs), taking place at approximately 0.5 eV (1.0 eV) above the Fermi energy. Finally, an efficient hot electron generation and extraction can be achieved in nanofilms of Pd (110) and Pd (100) when subject to excitation energies ranging from 0.4 to 1.6 eV.
2019
C (Trovatello Trovatello, Chiara) ; Miranda
Strong Exciton-Coherent Phonon Coupling In Single-Layer MoS2 Proceedings Article
In: LASERS, 2019 CONFERENCE ON; (CLEO), ELECTRO-OPTICS (Ed.): Conference on Lasers and Electro-Optics, 2019, ISBN: 978-1-943580-57-6; ISSN 2160-9020.
Abstract | Links | BibTeX | Tags: Applied, Electric & Electronic, General Engineering, Optics, Physics
@inproceedings{nokey,
title = {Strong Exciton-Coherent Phonon Coupling In Single-Layer MoS2},
author = {Trovatello, C (Trovatello, Chiara) ; Miranda, HPC (Miranda, Henrique P. C.) ; Molina-Sánchez, A (Molina-Sanchez, Alejandro) ; Varillas, RB (Varillas, Rocio Borrego) ; Moretti, L (Moretti, Luca) ; Ganzer, L (Ganzer, Lucia) ; Maiuri, M (Maiuri, Margherita) ; Soavi, G (Soavi, Giancarlo) ; Ferrari, AC (Ferrari, Andrea C.) ; Marini, A (Marini, Andrea) ; Wirtz, L (Wirtz, Ludger) ; Cerullo, G (Cerullo, Giulio) ; Sangalli, D (Sangalli, Davide) ; Dal Conte, S (Dal Conte, Stefano)},
editor = {2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)},
url = {https://www.webofscience.com/wos/woscc/summary/6adb417d-7241-4ee4-a70c-46a96938e0e3-014078f410/relevance/1},
isbn = {978-1-943580-57-6; ISSN 2160-9020},
year = {2019},
date = {2019-09-09},
urldate = {2019-09-09},
booktitle = {Conference on Lasers and Electro-Optics},
abstract = {We use broadband optical pump-probe spectroscopy to study coherent optical phonons in 1L-MoS2. We detect a strong coupling with the A'(1) mode, which is enhanced around the C-exciton peak. Ab-initio calculations of the phonon-induced band structure variation fully confirm this result.},
keywords = {Applied, Electric & Electronic, General Engineering, Optics, Physics},
pubstate = {published},
tppubtype = {inproceedings}
}
We use broadband optical pump-probe spectroscopy to study coherent optical phonons in 1L-MoS2. We detect a strong coupling with the A'(1) mode, which is enhanced around the C-exciton peak. Ab-initio calculations of the phonon-induced band structure variation fully confirm this result.
D (Sangalli Sangalli, D. ) ; Ferretti
Many-body perturbation theory calculations using the yambo code Journal Article
In: JOURNAL OF PHYSICS-CONDENSED MATTER, vol. 31, iss. 32, no. 325902, 2019, ISSN: 0953-8984; eISSN 1361-648X.
Abstract | Links | BibTeX | Tags: Condensed matter, Physics
@article{nokey,
title = {Many-body perturbation theory calculations using the yambo code},
author = {Sangalli, D (Sangalli, D.) ; Ferretti, A (Ferretti, A.) ; Miranda, H (Miranda, H.) ; Attaccalite, C (Attaccalite, C.) ; Marri, I (Marri, I) ; Cannuccia, E (Cannuccia, E.) ; Melo, P (Melo, P.) ; Marsili, M (Marsili, M.) ; Paleari, F (Paleari, F.) ; Marrazzo, A (Marrazzo, A.) ; Prandini, G (Prandini, G.) ; Bonfà, P (Bonfa, P.) ; Atambo, MO (Atambo, M. O.) ; Affinito, F (Affinito, F.) ; Palummo, M (Palummo, M.) ; Molina-Sánchez, A (Molina-Sanchez, A.) ; Hogan, C (Hogan, C.) ; Grüning, M (Gruning, M.) ; Varsano, D (Varsano, D.) ; Marini, A (Marini, A.) },
editor = {IOP Publishing Ltd},
doi = {10.1088/1361-648X/ab15d0},
issn = {0953-8984; eISSN 1361-648X},
year = {2019},
date = {2019-08-14},
journal = {JOURNAL OF PHYSICS-CONDENSED MATTER},
volume = {31},
number = {325902},
issue = {32},
abstract = {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 independent-particle 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 oftneglected physical effects such as electron-phonon interactions to the implementation of a realtime propagation scheme for simulating linear and non-linear 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.},
keywords = {Condensed matter, Physics},
pubstate = {published},
tppubtype = {article}
}
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 independent-particle 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 oftneglected physical effects such as electron-phonon interactions to the implementation of a realtime propagation scheme for simulating linear and non-linear 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.
E (Perfetto Perfetto, E. ) ; Sangalli
First-Principles Nonequilibrium Green's Function Approach to Ultrafast Charge Migration in Glycine Journal Article
In: JOURNAL OF CHEMICAL THEORY AND COMPUTATION, vol. 15, iss. 8, pp. 4526-4534, 2019, ISSN: 1549-9618; eISSN 1549-9626.
Abstract | Links | BibTeX | Tags: Atomic and Molecular Physics, Chemistry, Physics
@article{nokey,
title = {First-Principles Nonequilibrium Green's Function Approach to Ultrafast Charge Migration in Glycine},
author = {Perfetto, E (Perfetto, E.) ; Sangalli, D (Sangalli, D.) ; Palummo, M (Palummo, M.) ; Marini, A (Marini, A.) ; Stefanucci, G (Stefanucci, G.)},
editor = {AMER CHEMICAL SOC},
doi = {10.1021/acs.jctc.9b00170},
issn = {1549-9618; eISSN 1549-9626},
year = {2019},
date = {2019-08-01},
urldate = {2019-08-01},
journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION},
volume = {15},
issue = {8},
pages = {4526-4534},
abstract = {We investigate the photoinduced ultrafast charge migration phenomenon in the glycine molecule using a recently proposed nonequilibrium Green's functions (NEGF) approach. We first consider the dynamics resulting from the sudden removal of an electron in the valence shells, finding a satisfactory agreement with available data. Then we explicitly simulate the laser-induced photoionization process and study the evolution of the system after the pulse. We disentangle polarization and correlation effects in the electron dynamics and assign the main frequencies to specific elements of the reduced one-particle density matrix. We show that electronic correlations renormalize the bare frequencies, redistribute the spectral weights, and give rise to new spectral features.},
keywords = {Atomic and Molecular Physics, Chemistry, Physics},
pubstate = {published},
tppubtype = {article}
}
We investigate the photoinduced ultrafast charge migration phenomenon in the glycine molecule using a recently proposed nonequilibrium Green's functions (NEGF) approach. We first consider the dynamics resulting from the sudden removal of an electron in the valence shells, finding a satisfactory agreement with available data. Then we explicitly simulate the laser-induced photoionization process and study the evolution of the system after the pulse. We disentangle polarization and correlation effects in the electron dynamics and assign the main frequencies to specific elements of the reduced one-particle density matrix. We show that electronic correlations renormalize the bare frequencies, redistribute the spectral weights, and give rise to new spectral features.
ZL (Wang Wang, Zilong) ; Molina-Sanchez
Real-time observation of the intravalley spin-flip process in single-layer WS2 Conference
EPJ Web of Conferences, vol. 205, no. 05012, Cerullo, G (Cerullo, G) ; Ogilvie, J (Ogilvie, J) ; Kartner, F (Kartner, F) ; Khalil, M (Khalil, M) ; Li, R (Li, R), 2019, ISSN: 2100-014X.
Abstract | Links | BibTeX | Tags: Chemistry, Condensed matter, Mechanics, Microscopy, Optics, Physics, Spectroscopy
@conference{nokey,
title = {Real-time observation of the intravalley spin-flip process in single-layer WS2},
author = {Wang, ZL (Wang, Zilong) ; Molina-Sanchez, A (Molina-Sanchez, Alejandro) ; Altmann, P (Altmann, Patrick) ; Sangalli, D (Sangalli, Davide) ; De Fazio, D (De Fazio, Domenico) ; Soavi, G (Soavi, Giancarlo) ; Sassi, U (Sassi, Ugo) ; Bottegoni, F (Bottegoni, Federico) ; Ciccacci, F (Ciccacci, Franco) ; Finazzi, M (Finazzi, Marco) ; Wirtz, L (Wirtz, Ludger) ; Ferrari, A (Ferrari, Andrea) ; Marini, A (Marini, Andrea) ; Cerullo, G (Cerullo, Giulio) ; Dal Conte, S (Dal Conte, Stefano) },
editor = {XXI INTERNATIONAL CONFERENCE ON ULTRAFAST PHENOMENA 2018 (UP 2018)},
doi = {10.1051/epjconf/201920505012},
issn = {2100-014X},
year = {2019},
date = {2019-01-01},
urldate = {2019-01-01},
booktitle = {EPJ Web of Conferences},
volume = {205},
number = {05012},
publisher = {Cerullo, G (Cerullo, G) ; Ogilvie, J (Ogilvie, J) ; Kartner, F (Kartner, F) ; Khalil, M (Khalil, M) ; Li, R (Li, R)},
abstract = {We use helicity-resolved transient absorption spectroscopy to track intravalley scattering dynamics in monolayer WS2. We find that spin-polarized carriers scatter from upper to lower conduction band by reversing their spin orientation on a sub-ps timescale.},
keywords = {Chemistry, Condensed matter, Mechanics, Microscopy, Optics, Physics, Spectroscopy},
pubstate = {published},
tppubtype = {conference}
}
We use helicity-resolved transient absorption spectroscopy to track intravalley scattering dynamics in monolayer WS2. We find that spin-polarized carriers scatter from upper to lower conduction band by reversing their spin orientation on a sub-ps timescale.
2018
ZL (Wang Wang, Zilong) ; Molina-Sánchez
Intravalley Spin-Flip Relaxation Dynamics in Single-Layer WS2 Journal Article
In: NANO LETTERS, vol. 18, iss. 11, pp. 6882-6891, 2018, ISSN: 1530-6984; eISSN 1530-6992.
Abstract | Links | BibTeX | Tags: Chemistry, Condensed matter, General Materials Science, Multidisciplinary, Nanoscience, Nanotechnology, Physics
@article{nokey,
title = {Intravalley Spin-Flip Relaxation Dynamics in Single-Layer WS2},
author = {Wang, ZL (Wang, Zilong) ; Molina-Sánchez, A (Molina-Sanchez, Alejandro) ; Altmann, P (Altmann, Patrick) ; Sangalli, D (Sangalli, Davide) ; De Fazio, D (De Fazio, Domenico) ; Soavi, G (Soavi, Giancarlo) ; Sassi, U (Sassi, Ugo) ; Bottegoni, F (Bottegoni, Federico) ; Ciccacci, F (Ciccacci, Franco) ; Finazzi, M (Finazzi, Marco) ; Wirtz, L (Wirtz, Ludger) ; Ferrari, AC (Ferrari, Andrea C.) ; Marini, A (Marini, Andrea) ; Cerullo, G (Cerullo, Giulio) ; Dal Conte, S (Dal Conte, Stefano)},
editor = {AMER CHEMICAL SOC},
doi = {10.1021/acs.nanolett.8b02774},
issn = {1530-6984; eISSN 1530-6992},
year = {2018},
date = {2018-11-01},
urldate = {2018-11-01},
journal = {NANO LETTERS},
volume = {18},
issue = {11},
pages = {6882-6891},
abstract = {In monolayer (1L) transition metal dichalcogenides (TMDs) the valence and conduction bands are spin-split because of the strong spin-orbit interaction. In tungsten-based TMDs the spin-ordering of the conduction band is such that the so-called dark excitons, consisting of electrons and holes with opposite spin orientation, have lower energy than A excitons. The transition from bright to dark excitons involves the scattering of electrons from the upper to the lower conduction band at the K point of the Brillouin zone, with detrimental effects for the optoelectronic response of 1L-TMDs, since this reduces their light emission efficiency. Here, we exploit the valley selective optical selection rules and use two-color helicity-resolved pump-probe spectroscopy to directly measure the intravalley spin-flip relaxation dynamics in 1L-WS2. This occurs on a sub-ps time scale, and it is significantly dependent on temperature, indicative of phonon-assisted relaxation. Time-dependent ab initio calculations show that intravalley spin-flip scattering occurs on significantly longer time scales only at the K point, while the occupation of states away from the minimum of the conduction band significantly reduces the scattering time. Our results shed light on the scattering processes determining the light emission efficiency in optoelectronic and photonic devices based on 1L-TMDs.},
keywords = {Chemistry, Condensed matter, General Materials Science, Multidisciplinary, Nanoscience, Nanotechnology, Physics},
pubstate = {published},
tppubtype = {article}
}
In monolayer (1L) transition metal dichalcogenides (TMDs) the valence and conduction bands are spin-split because of the strong spin-orbit interaction. In tungsten-based TMDs the spin-ordering of the conduction band is such that the so-called dark excitons, consisting of electrons and holes with opposite spin orientation, have lower energy than A excitons. The transition from bright to dark excitons involves the scattering of electrons from the upper to the lower conduction band at the K point of the Brillouin zone, with detrimental effects for the optoelectronic response of 1L-TMDs, since this reduces their light emission efficiency. Here, we exploit the valley selective optical selection rules and use two-color helicity-resolved pump-probe spectroscopy to directly measure the intravalley spin-flip relaxation dynamics in 1L-WS2. This occurs on a sub-ps time scale, and it is significantly dependent on temperature, indicative of phonon-assisted relaxation. Time-dependent ab initio calculations show that intravalley spin-flip scattering occurs on significantly longer time scales only at the K point, while the occupation of states away from the minimum of the conduction band significantly reduces the scattering time. Our results shed light on the scattering processes determining the light emission efficiency in optoelectronic and photonic devices based on 1L-TMDs.
D (Sangalli Sangalli, Davide) ; Perfetto
An ab-initio approach to describe coherent and non-coherent exciton dynamics Journal Article
In: EUROPEAN PHYSICAL JOURNAL B, vol. 91, iss. 8, no. 171, 2018, ISSN: 1434-6028; eISSN 1434-6036.
Abstract | Links | BibTeX | Tags: Condensed matter, Physics
@article{nokey,
title = {An ab-initio approach to describe coherent and non-coherent exciton dynamics},
author = {Sangalli, D (Sangalli, Davide) ; Perfetto, E (Perfetto, Enrico) ; Stefanucci, G (Stefanucci, Gianluca) ; Marini, A (Marini, Andrea)},
doi = {10.1140/epjb/e2018-90126-5},
issn = {1434-6028; eISSN 1434-6036},
year = {2018},
date = {2018-08-01},
urldate = {2018-08-01},
journal = { EUROPEAN PHYSICAL JOURNAL B},
volume = {91},
number = {171},
issue = {8},
abstract = {The use of ultra-short laser pulses to pump and probe materials activates a wealth of processes which involve the coherent and non coherent dynamics of interacting electrons out of equilibrium. Non equilibrium (NEQ) many body perturbation theory (MBPT) offers an equation of motion for the density- matrix of the system which well describes both coherent and non coherent processes. In the non correlated case there is a clear relation between these two regimes and the matrix elements of the density-matrix. The same is not true for the correlated case, where the potential binding of electrons and holes in excitonic states need to be considered. In the present work we discuss how NEQ-MBPT can be used to describe the dynamics of both coherent and non-coherent excitons in the low density regime. The approach presented is well suited for an ab initio implementation.},
keywords = {Condensed matter, Physics},
pubstate = {published},
tppubtype = {article}
}
The use of ultra-short laser pulses to pump and probe materials activates a wealth of processes which involve the coherent and non coherent dynamics of interacting electrons out of equilibrium. Non equilibrium (NEQ) many body perturbation theory (MBPT) offers an equation of motion for the density- matrix of the system which well describes both coherent and non coherent processes. In the non correlated case there is a clear relation between these two regimes and the matrix elements of the density-matrix. The same is not true for the correlated case, where the potential binding of electrons and holes in excitonic states need to be considered. In the present work we discuss how NEQ-MBPT can be used to describe the dynamics of both coherent and non-coherent excitons in the low density regime. The approach presented is well suited for an ab initio implementation.
A (Seidu Seidu, Azimatu) ; Marini
Dynamical correlation effects in a weakly correlated material: Inelastic x-ray scattering and photoemission spectra of beryllium Bachelor Thesis
2018, ISSN: 2469-9950; eISSN 2469-9969.
Abstract | Links | BibTeX | Tags: Condensed matter, General Materials Science, Multidisciplinary, Physics
@bachelorthesis{nokey,
title = {Dynamical correlation effects in a weakly correlated material: Inelastic x-ray scattering and photoemission spectra of beryllium},
author = {Seidu, A (Seidu, Azimatu) ; Marini, A (Marini, Andrea) ; Gatti, M (Gatti, Matteo)},
editor = {AMER PHYSICAL SOC},
doi = {10.1103/PhysRevB.97.125144},
issn = {2469-9950; eISSN 2469-9969},
year = {2018},
date = {2018-03-26},
urldate = {2018-03-26},
journal = {Physical Review B},
volume = {97},
number = {125144},
issue = {12},
abstract = {Beryllium is a weakly correlated simple metal. Still we find that dynamical correlation effects, beyond the independent-particle picture, are necessary to successfully interpret the electronic spectra measured by inelastic x-ray scattering (IXS) and photoemission spectroscopies (PES). By combining ab initio time-dependent density-functional theory (TDDFT) and many-body Green's function theory in the GW approximation (GWA), we calculate the dynamic structure factor, the quasiparticle (QP) properties and PES spectra of bulk Be. We show that band-structure effects (i.e., due to interaction with the crystal potential) and QP lifetimes (LT) are both needed in order to explain the origin of the measured double-peak features in the IXS spectra. A quantitative agreement with experiment is obtained only when LT are supplemented to the adiabatic local-density approximation (ALDA) of TDDFT. Besides the valence band, PES spectra display a satellite, a signature of dynamical correlation due to the coupling of QPs and plasmons, which we are able to reproduce thanks to the combination of the GWA for the self-energy with the cumulant expansion of the Green's function.},
keywords = {Condensed matter, General Materials Science, Multidisciplinary, Physics},
pubstate = {published},
tppubtype = {bachelorthesis}
}
Beryllium is a weakly correlated simple metal. Still we find that dynamical correlation effects, beyond the independent-particle picture, are necessary to successfully interpret the electronic spectra measured by inelastic x-ray scattering (IXS) and photoemission spectroscopies (PES). By combining ab initio time-dependent density-functional theory (TDDFT) and many-body Green's function theory in the GW approximation (GWA), we calculate the dynamic structure factor, the quasiparticle (QP) properties and PES spectra of bulk Be. We show that band-structure effects (i.e., due to interaction with the crystal potential) and QP lifetimes (LT) are both needed in order to explain the origin of the measured double-peak features in the IXS spectra. A quantitative agreement with experiment is obtained only when LT are supplemented to the adiabatic local-density approximation (ALDA) of TDDFT. Besides the valence band, PES spectra display a satellite, a signature of dynamical correlation due to the coupling of QPs and plasmons, which we are able to reproduce thanks to the combination of the GWA for the self-energy with the cumulant expansion of the Green's function.
E (Perfetto Perfetto, E. ) ; Sangalli
Ultrafast Charge Migration in XUV Photoexcited Phenylalanine: A First-Principles Study Based on Real-Time Nonequilibrium Green's Functions Journal Article
In: JOURNAL OF PHYSICAL CHEMISTRY LETTERS, vol. 9, iss. 6, pp. 1353-1358, 2018, ISSN: 1948-7185.
Abstract | Links | BibTeX | Tags: Atomic and Molecular Physics, Chemistry, General Materials Science, Nanoscience, Nanotechnology, Physics
@article{nokey,
title = {Ultrafast Charge Migration in XUV Photoexcited Phenylalanine: A First-Principles Study Based on Real-Time Nonequilibrium Green's Functions},
author = {Perfetto, E (Perfetto, E.) ; Sangalli, D (Sangalli, D.) ; Marini, A (Marini, A.) ; Stefanucci, G (Stefanucci, G.)},
editor = {AMER CHEMICAL SOC},
doi = {10.1021/acs.jpclett.8b00025},
issn = {1948-7185},
year = {2018},
date = {2018-03-15},
urldate = {2018-03-15},
journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS},
volume = {9},
issue = {6},
pages = {1353-1358},
abstract = {The early-stage density oscillations of the electronic charge in molecules irradiated by an attosecond XUV pulse takes place on femto- or subfemtosecond time scales. This ultrafast charge migration process is a central topic in attoscience because it dictates the relaxation pathways of the molecular structure. A predictive quantum theory of ultrafast charge migration should incorporate the atomistic details of the molecule, electronic correlations, and the multitude of ionization channels activated by the broad-bandwidth XUV pulse. We propose a first-principles nonequilibrium Green's function method fulfilling all three requirements and apply it to a recent experiment on the photoexcited phenylalanine amino acid. Our results show that dynamical correlations are necessary for a quantitative overall agreement with the experimental data. In particular, we are able to capture the transient oscillations at frequencies 0.15 and 0.30 PHz in the hole density of the amine group as well as their suppression and the concomitant development of a new oscillation at frequency 0.25 PHz after similar to 14 fs.},
keywords = {Atomic and Molecular Physics, Chemistry, General Materials Science, Nanoscience, Nanotechnology, Physics},
pubstate = {published},
tppubtype = {article}
}
The early-stage density oscillations of the electronic charge in molecules irradiated by an attosecond XUV pulse takes place on femto- or subfemtosecond time scales. This ultrafast charge migration process is a central topic in attoscience because it dictates the relaxation pathways of the molecular structure. A predictive quantum theory of ultrafast charge migration should incorporate the atomistic details of the molecule, electronic correlations, and the multitude of ionization channels activated by the broad-bandwidth XUV pulse. We propose a first-principles nonequilibrium Green's function method fulfilling all three requirements and apply it to a recent experiment on the photoexcited phenylalanine amino acid. Our results show that dynamical correlations are necessary for a quantitative overall agreement with the experimental data. In particular, we are able to capture the transient oscillations at frequencies 0.15 and 0.30 PHz in the hole density of the amine group as well as their suppression and the concomitant development of a new oscillation at frequency 0.25 PHz after similar to 14 fs.
2017
A (Molina-Sanchez Molina-Sánchez, Alejandro) ; Sangalli
Ab Initio Calculations of Ultrashort Carrier Dynamics in Two-Dimensional Materials: Valley Depolarization in Single-Layer WSe2 Journal Article
In: NANO LETTERS, vol. 17, iss. 8, pp. 4549-4555, 2017, ISSN: 1530-6984; eISSN 1530-6992.
Abstract | Links | BibTeX | Tags: Chemistry, Condensed matter, General Materials Science, Multidisciplinary, Nanoscience, Nanotechnology, Physics
@article{nokey,
title = {Ab Initio Calculations of Ultrashort Carrier Dynamics in Two-Dimensional Materials: Valley Depolarization in Single-Layer WSe2},
author = {Molina-Sánchez, A (Molina-Sanchez, Alejandro) ; Sangalli, D (Sangalli, Davide) ; Wirtz, L (Wirtz, Ludger) ; Marini, A (Marini, Andrea)},
editor = {AMER CHEMICAL SOC},
doi = {10.1021/acs.nanolett.7b00175},
issn = {1530-6984; eISSN 1530-6992},
year = {2017},
date = {2017-08-01},
urldate = {2017-08-01},
journal = {NANO LETTERS},
volume = {17},
issue = {8},
pages = {4549-4555},
abstract = {In single-layer WSe2, a paradigmatic semi-conducting transition metal dichalcogenide, a circularly polarized laser field can selectively excite electronic transitions in one of the inequivalent K-+/- valleys. Such selective valley population corresponds to a pseudospin polarization. This can be used as a degree of freedom in a "valleytronic" device provided that the time scale for its depolarization is sufficiently large. Yet, the mechanism behind the valley depolarization still remains heavily debated. Recent time-dependent Kerr experiments have provided an accurate way to visualize the valley dynamics by measuring the rotation of a linearly polarized probe pulse applied after a circularly polarized pump pulse. We present here a clear, accurate and parameter-free description of the valley dynamics. By using an atomistic, ab initio approach, we fully, disclose the elemental mechanisms that dictate the depolarization effects. Our results are in excellent agreement with recent time dependent Kerr experiments. We explain the Kerr dynamics and its temperature dependence in terms of electron-phonon-mediated processes that induce spin-flip intervalley transitions.},
keywords = {Chemistry, Condensed matter, General Materials Science, Multidisciplinary, Nanoscience, Nanotechnology, Physics},
pubstate = {published},
tppubtype = {article}
}
In single-layer WSe2, a paradigmatic semi-conducting transition metal dichalcogenide, a circularly polarized laser field can selectively excite electronic transitions in one of the inequivalent K-+/- valleys. Such selective valley population corresponds to a pseudospin polarization. This can be used as a degree of freedom in a "valleytronic" device provided that the time scale for its depolarization is sufficiently large. Yet, the mechanism behind the valley depolarization still remains heavily debated. Recent time-dependent Kerr experiments have provided an accurate way to visualize the valley dynamics by measuring the rotation of a linearly polarized probe pulse applied after a circularly polarized pump pulse. We present here a clear, accurate and parameter-free description of the valley dynamics. By using an atomistic, ab initio approach, we fully, disclose the elemental mechanisms that dictate the depolarization effects. Our results are in excellent agreement with recent time dependent Kerr experiments. We explain the Kerr dynamics and its temperature dependence in terms of electron-phonon-mediated processes that induce spin-flip intervalley transitions.
0000
Marini, Andrea
Dynamical electron-phonon vertex correction Journal Article Forthcoming
In: Condensed Matter, Forthcoming, ISSN: 2501.01866.
Abstract | Links | BibTeX | Tags: Atomic and Molecular Physics, Condensed matter, General Physics and Astronomy, Optics, Physics
@article{nokey,
title = {Dynamical electron-phonon vertex correction},
author = {Andrea Marini},
editor = {Cornell University},
url = {https://arxiv.org/pdf/2501.01866},
doi = { https://doi.org/10.48550/arXiv.2501.01866},
issn = {2501.01866},
journal = {Condensed Matter},
abstract = {The dynamical screening of the electron--phonon vertex is caused by the retarded oscillations of the electronic charge following the electron--hole scattering with a phonon mode. This retardation induces a frequency dependence of the electron--phonon interaction. Model Hamiltonians and {em ab--initio} approaches have instilled the idea that this retardation is, in most of the cases, negligible. In this work I demonstrate that the dynamical screening of the electron--phonon vertex cannot be neglected {em a priori}. By using a perturbative expansion I introduce a controllable and physically sound method to evaluate and include dynamical screening effects. Based on the exact results of the homogeneous electron gas I propose a dynamical vertex correction function Γe−p(ω) designed to screen the commonly used adiabatic electron--phonon interaction. This function is expressed in terms of adiabatic quantities, that can be easily calculated and used to evaluate the strength of the dynamical corrections, even in realistic materials.},
keywords = {Atomic and Molecular Physics, Condensed matter, General Physics and Astronomy, Optics, Physics},
pubstate = {forthcoming},
tppubtype = {article}
}
The dynamical screening of the electron--phonon vertex is caused by the retarded oscillations of the electronic charge following the electron--hole scattering with a phonon mode. This retardation induces a frequency dependence of the electron--phonon interaction. Model Hamiltonians and {em ab--initio} approaches have instilled the idea that this retardation is, in most of the cases, negligible. In this work I demonstrate that the dynamical screening of the electron--phonon vertex cannot be neglected {em a priori}. By using a perturbative expansion I introduce a controllable and physically sound method to evaluate and include dynamical screening effects. Based on the exact results of the homogeneous electron gas I propose a dynamical vertex correction function Γe−p(ω) designed to screen the commonly used adiabatic electron--phonon interaction. This function is expressed in terms of adiabatic quantities, that can be easily calculated and used to evaluate the strength of the dynamical corrections, even in realistic materials.
