Understanding the mutual interaction between electronic excitations and lattice vibrations is key for understanding electronic transport and optoelectronic phenomena. Dynamic manipulation of such interaction is elusive because it requires varying the material composition on the atomic level. In turn, recent studies on topological insulators (TIs) have revealed the coexistence of a strong phonon resonance and topologically protected Dirac plasmon, both in the terahertz (THz) frequency range. Here, using these intrinsic characteristics of TIs, we demonstrate a new methodology for controlling electron-phonon interaction by lithographically engineered Dirac surface plasmons in the Bi2Se3 TI. Through a series of time-domain and time-resolved ultrafast THz measurements, we show that, when the Dirac plasmon energy is less than the TI phonon energy, the electron-phonon coupling is trivial, exhibiting phonon broadening associated with Landau damping. In contrast, when the Dirac plasmon energy exceeds that of the phonon resonance, we observe suppressed electron-phonon interaction leading to unexpected phonon stiffening. Time-dependent analysis of the Dirac plasmon behavior, phonon broadening, and phonon stiffening reveals a transition between the distinct dynamics corresponding to the two regimes as the Dirac plasmon resonance moves across the TI phonon resonance, which demonstrates the capability of Dirac plasmon control. Our results suggest that the engineering of Dirac plasmons provides a new alternative for controlling the dynamic interaction between Dirac carriers and phonons.
Bibliographical noteFunding Information:
C.I., S.S., B.K., H.B., and H.C. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (grant nos. NRF-2016R1A4A1012929 and NRF-2015R1A2A1A10052520) and the Global Frontier Program (grant no. 2014M3A6B3063709). H.J., W.J., M.S., A.S., M.-H.H., and H.L. were supported by NRF through MSIP (grant no. NRF-2016R1A4A1012929). C.I., S.S., B.K., H.B., M.S., M.-H.H., and H.C. were supported by Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (grant no. 2017M3D1A1040828). C.I. was supported by NRF through MSIP (grant no. NRF-2015H1A2A1034809). J.M., M.S., and S.O. were supported by Gordon and Betty Moore Foundation's EPiQS Initiative (grant no. GBMF4418) and the National Science Foundation (NSF) (grant no. EFMA-1542798). S.Y.S. and M.-H.J. were supported by the Institute for Basic Science (IBS), Korea, under the Project Code no. IBSR014-A1-2017-a00.
© 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering