### Abstract

The picture of how a gap closes in a semiconductor has been radically transformed by topological concepts. Instead of the gap closing and immediately reopening, topological arguments predict that, in the absence of inversion symmetry, a metallic phase protected by Weyl nodes persists over a finite interval of the tuning parameter (for example, pressure P). The gap reappears when the Weyl nodes mutually annihilate. We report evidence that Pb_{1-x}Sn_{x}Te exhibits this topological metallic phase. Using pressure to tune the gap, we have tracked the nucleation of a Fermi surface droplet that rapidly grows in volume with P. In the metallic state, we observe a large Berry curvature, which dominates the Hall effect. Moreover, a giant negative magnetoresistance is observed in the insulating side of phase boundaries, in accord with ab initio calculations. The results confirm the existence of a topological metallic phase over a finite pressure interval.

Original language | English (US) |
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Article number | e1602510 |

Journal | Science Advances |

Volume | 3 |

Issue number | 5 |

DOIs | |

State | Published - May 2017 |

### All Science Journal Classification (ASJC) codes

- General

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## Cite this

_{1-x}Sn

_{x}Te.

*Science Advances*,

*3*(5), [e1602510]. https://doi.org/10.1126/sciadv.1602510