Rabia Sultana

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi 2 Te 3 Topological Insulator

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi2Te3 crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi2Te3 crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of − 0.5 to − 1.5. In our case, the low-field (± 0.25 T) fitting of studied crystal exhibited a value of α close to − 0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (lφ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi2Te3 follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio.

Unexplored photoluminescence from bulk and mechanically exfoliated few layers of Bi 2 Te 3

We report the exotic photoluminescence (PL) behaviour of 3D topological insulator Bi2Te3 single crystals grown by customized self-flux method and mechanically exfoliated few layers (18 ± 2 nm)/thin flakes obtained by standard scotch tape method from as grown Bi2Te3 crystals. The experimental PL studies on bulk single crystal and mechanically exfoliated few layers of Bi2Te3 evidenced a broad red emission in the visible region from 600–690 nm upon 375 nm excitation wavelength corresponding to optical band gap of 2 eV. These findings are in good agreement with our theoretical results obtained using the ab initio density functional theory framework. Interestingly, the observed optical band gap is several times larger than the known electronic band gap of ~0.15 eV. The experimentally observed 2 eV optical band gap in the visible region for bulk as well as for mechanically exfoliated few layers Bi2Te3 single crystals clearly rules out the quantum confinement effects in the investigated samples which are well known in the 2D systems like MoS2,WS2, WSe2, and MoSe2 for 1–3 layers.