Ultrashort Pulses to Probe Tunable Topological Surfaces and Applications

Mahendra, K. (2019) Ultrashort Pulses to Probe Tunable Topological Surfaces and Applications. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Mahendra K. (14MS001)) 14MS001.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

Topological Insulators are exotic class of new materials which have bulk insulating and surface conducting properties. Their low energy excitations are represented by mass-less Dirac electrons which have linear energy momentum dispersion relation. The time reversal symmetry and strong spin orbit coupling give rise to quantum states called topological surface states which gives them many unique abilities such as protection against back scattering, high mobility and tunable density. These properties attract them as one of the leading contenders for spintronics, quantum computation and many plasmonic applications. Lately ultrafast laser are becoming highly prevalent as tools to study materials for very short time-scales. This helps us charecterise materials depending on thier transient response and futher relaxation to stimulus in such timescales, which are important to judge the potential of said materials in various applications such as faast-response devices and such. We charecterise our Laser then probe Bi₂Te₃ and BSTS Single crystal in this study.We find Optical and Acoustic Phonons by Pump-Probe Spectroscopy in the samples investigated. We study the time scales of relaxation of the materials in question as a function of pump fluence. A qualitave interpretation of the material behavior is presented using availabe literature.

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