Authors: Xingquan Zou1, Jingzhi Shang1, Jianing Leaw1, Zhiqiang Luo1, Liyan Luo1, Chan La-o-vorakiat1, Liang Cheng1, S. A. Cheong1, Haibin Su2, Jian-Xin Zhu3, Yanpeng Liu4, Kian Ping Loh4, A. H. Castro Neto5, Ting Yu1, and Elbert E. M. Chia1
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
- Division of Materials Science, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
- Theoretical Division and Center for Integrated Nanotechnologies, +Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Department of Chemistry, +National University of Singapore , 3 Science Drive 3, 117543 Singapore
- Graphene Research Centre and Physics Department, National University of Singapore, 6 Science Drive 2, 117546 Singapore
AbstractUsing terahertz time-domain spectroscopy, the real part of optical conductivity [σ1(ω)] of twisted bilayer graphene was obtained at different temperatures (10–300 K) in the frequency range 0.3–3 THz. On top of a Drude-like response, we see a strong peak in σ1(ω) at ∼2.7 THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the peak at 2.7 THz to an enhanced density of states at that energy, which is caused by the presence of a van Hove singularity arising from a commensurate twisting of the two graphene layers.
© 2013 +American Physical Society
... The transmission THz spectra of the BLG were measured using a conventional THz-TDS system (TeraView TPS Spectra 3000)... THz TDS has proven to be a very useful noncontact technique to study material properties such as dielectric response, complex conductivity and refractive index in the far-infrared range without the need for Kramers-Kronig analysis ...