# Intertwined Topological Phases in TaAs2 Nanowires with Giant Magnetoresistance and Quantum Coherent Surface Transport

## TL;DR

TaAs2 nanowires show unique quantum effects like giant magnetoresistance and surface transport, offering potential for spintronics and quantum tech.

## Contribution

Synthesis of SiO2-encapsulated TaAs2 nanowires reveals intertwined topological phases with high-temperature transport features.

## Key findings

- TaAs2 nanowires exhibit a metal-to-insulator transition near room temperature.
- Aharonov–Bohm oscillations show coherent surface transport from WTI surface Dirac cones.
- Giant magnetoresistance with sign reversal and chiral anomaly is observed in these nanowires.

## 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.

Synthesis of topological semimetal TaAs2 nanowires in situ encapsulated with a thin SiO2 shell unravel a richness of intertwined topological phases manifested by their magnetotransport features: A near‐room‐temperature metal‐to‐insulator transition, strong expressions of topologically nontrivial surface transport, giant magnetoresistance with direction‐dependent sign reversal, chiral anomaly, and a unique double pattern of Aharonov–Bohm oscillations.