Topological Crystalline Transition Metals: Strained W, Ta, Mo, and Nb

TL;DR

This study demonstrates that strained transition metals W, Ta, Mo, and Nb host topologically protected surface states due to mirror symmetry, expanding the class of topologically nontrivial materials with potential applications in electronics.

Contribution

It introduces topological crystalline phases in transition metals with strain, supported by combined theoretical calculations and experimental evidence.

Findings

W(110) surface states confirmed as topologically protected

Experimental spin-resolved inverse photoemission detects nontrivial surface states in Ta(110)

Theoretical calculations agree with experimental results on topological invariants

Abstract

In a joint theoretical and experimental investigation we show that a series of transition metals with strained body-centered cubic lattice ---W, Ta, Nb, and Mo--- host surface states that are topologically protected by mirror symmetry. Our finding extends the class of topologically nontrivial systems by topological crystalline transition metals. The investigation is based on independent calculations of the electronic structures and of topological invariants, the results of which agree with established properties of the Dirac-type surface state in W(110). To further support our prediction, we investigate both experimentally by spin-resolved inverse photoemission and theoretically an unoccupied topologically nontrivial surface state in Ta(110).