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Multiphoton emission of electrons has been observed from sharp tips of heavily p-doped GaAs caused by laser pulses with, nominally, 800-nm wavelength, 1-nJ/pulse energy, and 90-fs duration. The emission is mostly due to four-photon processes, with some contribution from three-photon absorption as well. When the electron emission current due to two pulses separated by delay 200 fs << τ << 1 ns is integrated over all electron energies, it is less than that observed for the sum of the emission from the two individual pulses. This subadditive behavior is consistent with a fast electron emission process, i.e., one in which the electron emission occurs over a time comparable to the laser pulse width. The subadditivity results from Pauli blocking of electron emission by the second pulse due to a population increase of the GaAs conduction band caused by the first pulse. Such subadditive photoemission is a sensitive probe of excited-carrier dynamics. We employ the use of an excited-level population model to characterize the photon absorption process and give us a clearer understanding of the electron dynamics in GaAs associated with multiphoton electron emission. Possible applications of this subadditivity effect to control photoemitted electron spin are discussed.
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Site-selective doublon-holon dynamics in a pumped one-dimensional Hubbard superlattice with staggered Coulomb interactions
Doublon-holon dynamics is investigated in a pumped one-dimensional Hubbard model with a staggered on-site Coulomb interaction at half-filling. When the system parameters are set to be in the Mott-insulating regime the equilibrium sublattice density of states exhibits several characteristic peaks, corresponding to the lower and upper Hubbard bands as well as hybridization bands. We study the linear absorption spectrum and find two main peaks characterizing the photon frequencies which excite the ground state to an excited state. For a system driven by a laser pulse with general intensity and frequency, both the energy absorption and the doublon-holon dynamics exhibit distinct behaviors as a function of laser amplitude and frequency. Single-photon processes are observed at low laser intensity where the energy is absorbed for resonant laser frequencies. For strong laser intensity multiphoton-induced dynamics are observed in the system that are confirmed by an evaluation of the Loschmidt amplitude. The contribution of multiphoton processes to site-resolved double occupancy is also characterized by the generalized Loschmidt amplitude. The site-resolved doublon-holon dynamics are observed in both the one and multiphoton processes and the site-resolved behavior is explained within a quasiparticle picture. Our study suggests strategies to optically engineer the doublon-holon dynamics in one-dimensional strongly correlated many-body systems.
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- Award ID(s):
- 2114825
- PAR ID:
- 10554359
- Publisher / Repository:
- American Physical Society, PRB
- Date Published:
- Journal Name:
- Physical Review B
- Volume:
- 109
- Issue:
- 19
- ISSN:
- 2469-9950
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1103/PhysRevB.109.195121
