Interband resonant high-harmonic generation by valley polarized electron-hole pairs

Naotaka Yoshikawa, Kohei Nagai, Yuhei Takaguchi, Shogo Sasaki, Yasumitsu Miyata, and Koichiro Tanaka

Feb 14, 2019

Received Date: 4th February 19

We demonstrated nonperturbative high harmonics induced by intense mid-infrared light up to 18th order that well exceed the material bandgap in monolayer transition metal dichalcogenides. The intensities of the even-order high-harmonic radiation did not monotonically decrease as the harmonic order increased. By comparing the high harmonic spectra with the optical absorption spectra, we found that the enhancement in the high harmonics could be attributed to the resonance to the band nesting energy. We extended the three-step model for electron-hole pairs in solids into one that takes account of the possibility of a wave packet of Bloch electrons occupying any lattice site in real space. The calculation shows that the electron-hole pairs driven to the band nesting region significantly contribute to the high harmonic radiation, and the valley polarization and anisotropic band structure lead to polarization of the high-harmonic radiation. Our findings indicate that the nonlinear interband polarization significantly contributes to the generation of high harmonics in solids and opens the way for attosecond science with monolayer materials having widely tunable electronic structures.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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