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Ginsberg JS, Jadidi MM, Zhang J, Chen CY, Tancogne-Dejean N, Chae SH, Patwardhan GN, Xian L, Watanabe K, Taniguchi T, Hone J, Rubio A, Gaeta AL. Phonon-enhanced nonlinearities in hexagonal boron nitride. Nat Commun 2023; 14:7685. [PMID: 38001087 PMCID: PMC10673846 DOI: 10.1038/s41467-023-43501-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Polar crystals can be driven into collective oscillations by optical fields tuned to precise resonance frequencies. As the amplitude of the excited phonon modes increases, novel processes scaling non-linearly with the applied fields begin to contribute to the dynamics of the atomic system. Here we show two such optical nonlinearities that are induced and enhanced by the strong phonon resonance in the van der Waals crystal hexagonal boron nitride (hBN). We predict and observe large sub-picosecond duration signals due to four-wave mixing (FWM) during resonant excitation. The resulting FWM signal allows for time-resolved observation of the crystal motion. In addition, we observe enhancements of third-harmonic generation with resonant pumping at the hBN transverse optical phonon. Phonon-induced nonlinear enhancements are also predicted to yield large increases in high-harmonic efficiencies beyond the third.
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Affiliation(s)
- Jared S Ginsberg
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, NY, 10027, USA.
| | - M Mehdi Jadidi
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, NY, 10027, USA
| | - Jin Zhang
- Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg, 22761, Germany.
| | - Cecilia Y Chen
- Department of Electrical Engineering, Columbia University, New York, New York, NY, 10027, USA
| | - Nicolas Tancogne-Dejean
- Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg, 22761, Germany
| | - Sang Hoon Chae
- Department of Mechanical Engineering, Columbia University, New York, New York, NY, 10027, USA
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Gauri N Patwardhan
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, NY, 10027, USA
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Lede Xian
- Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg, 22761, Germany
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York, NY, 10027, USA
| | - Angel Rubio
- Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg, 22761, Germany.
- Center for Computational Quantum Physics, Simons Foundation Flatiron Institute, New York, NY, 10010, USA.
| | - Alexander L Gaeta
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, NY, 10027, USA.
- Department of Electrical Engineering, Columbia University, New York, New York, NY, 10027, USA.
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Neufeld O, Zhang J, De Giovannini U, Hübener H, Rubio A. Probing phonon dynamics with multidimensional high harmonic carrier-envelope-phase spectroscopy. Proc Natl Acad Sci U S A 2022; 119:e2204219119. [PMID: 35704757 PMCID: PMC9231615 DOI: 10.1073/pnas.2204219119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/12/2022] [Indexed: 11/18/2022] Open
Abstract
We explore pump-probe high harmonic generation (HHG) from monolayer hexagonal-boron-nitride, where a terahertz pump excites coherent optical phonons that are subsequently probed by an intense infrared pulse that drives HHG. We find, through state-of-the-art ab initio calculations, that the structure of the emission spectrum is attenuated by the presence of coherent phonons and no longer comprises discrete harmonic orders, but rather a continuous emission in the plateau region. The HHG yield strongly oscillates as a function of the pump-probe delay, corresponding to ultrafast changes in the lattice such as specific bond compression or stretching dynamics. We further show that in the regime where the excited phonon period and the pulse duration are of the same order of magnitude, the HHG process becomes sensitive to the carrier-envelope phase (CEP) of the driving field, even though the pulse duration is so long that no such sensitivity is observed in the absence of coherent phonons. The degree of CEP sensitivity versus pump-probe delay is shown to be a highly selective measure for instantaneous structural changes in the lattice, providing an approach for ultrafast multidimensional HHG spectroscopy. Remarkably, the obtained temporal resolution for phonon dynamics is ∼1 femtosecond, which is much shorter than the probe pulse duration because of the inherent subcycle contrast mechanism. Our work paves the way toward routes of probing phonons and ultrafast material structural changes with subcycle temporal resolution and provides a mechanism for controlling the HHG spectrum.
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Affiliation(s)
- Ofer Neufeld
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Jin Zhang
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Umberto De Giovannini
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Dipartimento di Fisica e Chimica—Emilio Segrè, Università degli Studi di Palermo, I-90123 Palermo Italy
| | - Hannes Hübener
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group, Universidad del País Vasco UPV/EHU, 20018 San Sebastián, Spain
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute, New York, NY 10010
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