Journal
NANO LETTERS
Volume 13, Issue 12, Pages 5797-5802Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl4021842
Keywords
Topological insulator; ultrafast optical pump mid-infrared probe spectroscopy; Dirac fermion dynamics; Dirac fermion-phonon coupling
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Funding
- National Science Council of the Republic of China, Taiwan [NSC101-2112-M-009-016-MY2, NSC 101-2112-M-009-017-MY2, NSC 102-2112-M-009-006-MY3, NSC101-2009-M-002-007]
- Grant MOE ATU Program at NCTU
- RFBR [12-02-33174 d]
- U.S. Department of Energy [DEAC02- 98CH10886]
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The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to 4 explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
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