# Quantum oscillations and nontrivial topological state in a compensated semimetal TaP2

## TL;DR

This study reveals that TaP2 exhibits nontrivial topological electronic states, large unsaturated magnetoresistance, and quantum oscillations, combining experimental magneto-transport data with ab initio calculations.

## Contribution

It provides the first comprehensive experimental and theoretical investigation of the topological properties and magnetotransport behavior of TaP2, a new transition-metal dipnictide.

## Key findings

- Observed unsaturated magnetoresistance of ~700% at 9 T and 2 K.
- Detected nonzero Berry phase indicating nontrivial band topology.
- Identified three fundamental magnetic oscillation frequencies consistent with theoretical Fermi surface calculations.

## Abstract

We report systematic magneto-transport measurements and ab initio calculations on single-crystalline TaP2, a new member of the transition-metal dipnictides. We observed unsaturated magnetoresistance (MR) reaching ~ 700% at a magnetic field (B) of 9 T at 2 K along with striking Shubnikov-de Hass (SdH) oscillations. Our analysis on the SdH oscillations reveals nonzero Berry phase, indicating nontrivial band topology. The analysis also uncovers three fundamental magnetic oscillation frequencies of 72 T, 237 T, and 356 T, consistent with the theoretical calculations which reveal one hole pocket and two electron pockets at the L point and one electron pocket at the Z point of the Brillouin zone. We also found negative longitudinal MR (n-MR) within a narrow window of the angles between B and the electric current (I). The n-MR could be fitted with the Adler-Bell-Jackiw chiral anomaly equation but the origin remains yet ambiguous. The ab inito calculations suggest TaP2 as a weak topological insulator with the Z2 indices of (0; 111), which exhibits topological surface states on the (001) surface.

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Source: https://tomesphere.com/paper/1905.13527