May 22, 2019
Tokyo Institute of Technology
Keio University
Associate Professor Kazutaka Nakamura and Project Professor Yosuke Kayanuma of the Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, along with Project Associate Professor Yutaka Shikano of the Graduate School of Science and Technology at Keio University, have revealed that in a semiconductor crystal irradiated with ultrashort light pulses, the collapse and revival of electronic coherence occurs due to quantum path interference in the optical transition process. They also demonstrated that the stimulated Raman process is dominant in the generation of coherent optical phonons, even in opaque regions.
They irradiated a semiconductor single crystal (n-type GaAs, or gallium arsenide) with a high-precision, time-controlled pair of femtosecond pulses and measured in real time the change in reflectivity caused by the generated coherent optical phonons. By varying the interval between the pulses with a precision of tens of attoseconds, they successfully achieved active control over the quantum superposition state of the electron and phonon states, observing the collapse and revival of electronic coherence.
Furthermore, by comparing their results with theoretical calculations based on the quantum theory of the elementary process of coherent optical phonon generation, they showed that the observed behavior of electronic coherence is due to the stimulated Raman process. This research is expected to enable high-precision quantum state control in solids.
The research findings were published online on May 20 (US Eastern Time) in the American Physical Society journal "Physical Review B" as a Rapid Communication and selected as an Editor's Suggestion.
For the full press release, please see the following.