Intertwined Topological Phases in TaAs 2 Nanowires with Giant Magnetoresistance and Quantum Coherent Surface Transport

Abstract

'Samuel D. Escribano' 'Olga Brontvein' 'Katya Rechav' 'Ora Bitton' 'Roni Ilan' 'Ernesto Joselevich'] Title: Abstract Nanowires (NWs) of topological materials are emerging as an exciting platform to probe and engineer new quantum phenomena that are hard to access in bulk phase. Their quasi-1D geometry and large surface-to-bulk ratio unlock new expressions of topology and highlight surface states. TaAs2, a compensated semimetal, is a topologically rich material harboring nodal-line, weak topological insulator (WTI), C2-protected topological crystalline insulator, and Zeeman field-induced Weyl semimetal phases. We report the synthesis of TaAs2 NWs in situ encapsulated in a dielectric SiO2 shell, which enable to probe rich magnetotransport phenomena, including metal-to-insulator transition and strong signatures of topologically nontrivial transport at remarkably high temperatures, direction-dependent giant positive, and negative magnetoresistance, and a double pattern of Aharonov-Bohm oscillations, demonstrating coherent surface transport consistent with the two Dirac cones of a WTI surface. The SiO2-encapsulated TaAs2 NWs show room-temperature conductivity up to 15 times higher than bulk TaAs2. The coexistence and susceptibility of topological phases to external stimuli have potential applications in spintronics and nanoscale quantum technology.