Weak-antilocalization and Surface Dominated Transport in Topological Insulator Bi2Se2Te

We explore the phase coherence of thin films of the topological insulator material Bi2Se2Te grown through pulsed laser deposition (PLD) technique. The films were characterised using various techniques for phase and composition. The films were found to be of good quality. We carried out extensive magneto-transport studies of these films and found that they exhibit two dimensional weak antilocalization behaviour. A careful analysis revealed a relatively high phase coherence length (58nm at 1.78K) for a PLD grown film. Since PLD is an inexpensive technique, with the possibility to integrate with other materials, one can make devices which can be extremely useful for low power spintronics and topological quantum computation.Comment: 16 page

Investigation of Thermodynamic Properties of Cu(NH3)4SO4.H2O, a Heisenberg Spin Chain Compound

Detailed experimental investigations of thermal and magnetic properties are presented for Cu(NH3)4SO4.H2O, an ideal uniform Heisenberg spin half chain compound. A comparison of these properties with relevant spin models is also presented. The temperature dependent magnetic susceptibility and specific heat data has been compared with the exact solution for uniform Heisenberg chain model derived by means of Bethe ansatz technique. Field dependent isothermal magnetization curves are simulated by Quantum Monte Carlo technique and compared with the corresponding experimental ones. Specific heat as a function of magnetic field (up to 7T) and temperature (down to 2K) is reported. Subsequently, the data are compared with the corresponding theoretical curves for the infinite Heisenberg spin half chain model with J=6K. Moreover, internal energy and entropy are calculated by analyzing the experimental specific heat data. Magnetic field and temperature dependent behavior of entropy and internal energy are in good agreement with the theoretical predictions