High Field Magneto-Conductivity Analysis of Bi2Se3 Single Crystal

We report the high field (up to 14Tesla) magneto-conductivity analysis of Bi2Se3 topological insulator grown via the self flux method. The detailed experimental investigations including crystal growth as well as the electrical, thermal and spectroscopic characterizations of the resultant Bi2Se3 single crystal are already reported by some of us. The current letter deals with high field magneto-conductivity analysis in terms of Hikami Larkin Nagaoka (HLN) model, which revealed that the electronic conduction is dominated by both surface states driven weak anti localization (WAL), as well the bulk WL (weak localization) states. Further, by applying the HLN equation we have extracted the fitting parameters i.e., phase coherence length and the pre-factor. The HLN equation exhibited values of [pre factor close to -1.0, indicating both WAL and WL contributions. On the other hand, the extracted phase coherence length is seen to decrease from 11.125 nm to 5.576 nm as the temperature is increased from 5K to 200K respectively. Summarily, the short letter discusses primarily the temperature dependent magneto-conductivity analysis of pristine Bi2Se3 single crystal by the HLN model.Comment: Letter to Editor MS: 10 pages including 3 Fig

Crystal Growth and Characterization of Bulk Sb2Te3Topological Insulator

The Sb2Te3 crystals are grown using the conventional self flux method via solid state reaction route, by melting constituent elements (Sb and Te) at high temperature (850 C), followed by slow cooling (2 C per hour).The weak anti localization (WAL) related low field (2 Tesla) magneto-conductance at low temperatures (2.5 K and 20 K) has been analysed and discussed using the Hikami- Larkin - Nagaoka (HLN) model. Summarily, the short letter reports an easy and versatile method for crystal growth of bulk Sb2Te3 topological insulator (TI) and its brief physical property characterization.Comment: 18 Pages Text + Figs: Accepted Mat. Res. Exp. (May 2018

Two-fold anisotropic superconducting state in topological superconductor Sn4_4Au

Here we report the anisotropic magnetotransport properties in the superconducting state of Sn$_4$Au single crystal. Sn$_4$Au single crystal is synthesized through an easy melt growth method. Superconducting properties are evidenced by resistivity vs. temperature and DC magnetization measurements. Isothermal magnetization measurements hint toward type-II superconductivity in Sn$_4$Au. In-plane and out-of-plane resistivity measurements show anisotropic behavior of the upper critical field at temperatures below superconducting transition (T$_c$ = 2.3 K). The observed anisotropy is more elucidated in resistivity measurements performed below Tc at different tilt angles. The anisotropy parameter is found to be 1.26. The observed results show the presence two-fold anisotropic superconducting state in Sn$_4$Au single crystal, which may be induced due to the layered structure of synthesized Sn$_4$Au single crystal.Comment: 10 Pages Text + Figs: Revised Submitted: Euro. Phys. Let

Hikami-Larkin-Nagaoka (HLN) treatment of the Magneto Conductivity of Bi2Te3 Topological Insulator

We report the magneto-conductivity analysis at different temperatures under magnetic field of up to 5Tesla 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 HLN (Hikami Larkin Nagaoka) equation and it is found that the conduction mechanism is dominated by both surface driven WAL (weak anti localization) and the bulk WL states. The value of HLN equation coefficient 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 (0.25Tesla) fitting of studied crystal exhibited value close to -0.86 for studied temperatures of up to 50K, indicating both WAL and WL contributions. The phase coherence length is found to decrease from 98.266 to 40.314nm 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.Comment: Short Letter MS 10 pages including 3 Figs: Letter J. Sup. & Novel Mag. (2018

High-Field Magneto-Conductivity Analysis of Bi2Se3 Single Crystal

We report the high-field (up to 14 Tesla) magneto-conductivity analysis of Bi2Se3 topological insulator grown via the self-flux method. The detailed experimental investigations including crystal growth as well as the electrical, thermal, and spectroscopic characterizations of the resultant Bi2Se3 single crystal are already reported by some of us. The current letter deals with high-field magneto-conductivity analysis in terms of Hikami Larkin Nagaoka (HLN) model, which revealed that the electronic conduction is dominated by both surface state-driven weak anti-localization (WAL), as well as the bulk weak localization (WL) states. Further, by applying the HLN equation, we have extracted the fitting parameters, i.e., phase coherence length (l(phi)) and the pre-factor (). Here, the magneto-conductivity data is fitted up to +/- 5 Tesla, but in order to extract reliable fitting parameters, the same is fitted at much lower magnetic fields, i.e., up to +/- 1 Tesla. The value of the HLN coefficient (), extracted from the HLN equation exhibited values close to - 1.0, indicating both WAL and WL contributions. On the other hand, the extracted is seen to decrease from 11.125 to 5.576 nm as the temperature is increased from 5 to 200 K, respectively. Summarily, the short letter discusses primarily the temperature-dependent magneto-conductivity analysis of pristine Bi2Se3 single crystal by the HLN model

Crystal growth and characterization of bulk Sb2Te3 topological insulator

The Sb2Te3 crystals are grown using the conventional self flux method via solid state reaction route, by melting constituent elements (Sb and Te) at high temperature (850 degrees C), followed by slow cooling (2 degrees C/h). As grown Sb2Te3 crystals are analysed for various physical properties by x-ray diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) coupled with Energy Dispersive x-ray Spectroscopy (EDAX) and electrical measurements under magnetic field (6 Tesla) down to low temperature (2.5 K). The XRD pattern revealed the growth of synthesized Sb2Te3 sample along (001) plane, whereas the SEM along with EDAX measurements displayed the layered structure with near stoichiometric composition, without foreign contamination. The Raman scattering studies displayed known (A(1g)(1), E-g(2) and A(1g)(2)) vibrational modes for the studied Sb2Te3. The temperature dependent electrical resistivity measurements illustrated the metallic nature of the as grown Sb2Te3 single crystal. Further, the magneto-transport studies represented linear positive magneto-resistance (MR) reaching up to 80% at 2.5 Kunder an applied field of 6 Tesla. The weak anti localization (WAL) related low field (+/- 2 Tesla) magneto-conductance at low temperatures (2.5 K and 20 K) has been analysed and discussed using the Hikami-Larkin-Nagaoka (HLN) model. Summarily, the short letter reports an easy and versatile method for crystal growth of bulk Sb2Te3 topological insulator(TI) and its brief physical property characterization

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi2Te3 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 (alpha) 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 alpha close to - 0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (l (phi) ) 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

Efficient Synthesis of Impurity-C of Antimigraine Agent Rizatriptan Benzoate

During the commercial manufacturing of antimigraine drug Rizatriptan benzoate, several impurities are reported to be formed. This present work demonstrates a convergent and short synthesis of the most critical impurity (C) of Rizatriptan, [2-(5-((1H-1,2,4-triazol-1-yl)­methyl)-1H-indole-2-yl)-<i>N</i>,<i>N</i>-dimethylethanamine (<b>1</b>)], recently reported in U.S. Pharmacopeia