Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 117, Issue 16, Pages 8788-8793Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1917341117
Keywords
charge-density wave; electron-phonon interactions; ultrafast science; ARPES
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Funding
- National Science Foundation through the JILA Physics Frontiers Center [PHY1125844]
- Gordon and Betty Moore Foundation EPiQS Award [GBMF4538]
- National Natural Science Foundation of China [11874121]
- Swedish Research Council (Vetenskapsradet, VR)
- K. and A. Wallenberg Foundation [2015.0060]
- Swedish National Infrastructure for Computing
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Ultrashort light pulses can selectively excite charges, spins, and phonons in materials, providing a powerful approach for manipulating their properties. Here we use femtosecond laser pulses to coherently manipulate the electron and phonon distributions, and their couplings, in the charge-density wave (CDW) material 1T-TaSe2. After exciting the material with a femtosecond pulse, fast spatial smearing of the laser-excited electrons launches a coherent lattice breathing mode, which in turn modulates the electron temperature. This finding is in contrast to all previous observations in multiple materials to date, where the electron temperature decreases monotonically via electron-phonon scattering. By tuning the laser fluence, the magnitude of the electron temperature modulation changes from similar to 200 K in the case of weak excitation, to similar to 1,000 K for strong laser excitation. We also observe a phase change of pi in the electron temperature modulation at a critical fluence of 0.7 mJ/cm(2), which suggests a switching of the dominant coupling mechanism between the coherent phonon and electrons. Our approach opens up routes for coherently manipulating the interactions and properties of two-dimensional and other quantum materials using light.
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