Engineering topological surface states through structural control, electrostatic gating and superconducting proximity effects

Abstract

Three dimensional topological insulators are materials characterized by a gapped insulating bulk and gapless metallic states on the sample surface. This unique be- havior arises out of the non-trivial topology of the bulk band structure and lends a host of exotic properties to such materials. Speci fically, surface states in topo- logical insulators are described by spin-helical Dirac fermions where the direction of spin is locked to its momentum. A rich spectrum of exotic physical phenomena are predicted to arise from the manipulation of topological surface states and their response to disorder, interactions, magnetic and superconducting order. Experi- mentally, however, robust access to topological surface states has presented itself as a formidable challenge. Even after a decade of their discovery, topological insula- tors remain arcane materials and their surface states remain elusive to experimental detection and manipulation. In this thesis, we solve this problem and achieve un- precedented control over topological surface states, enable their manipulation using electrostatic gating and study their response to proximity induced superconducting order.