Dual topological superconducting states in the layered titanium-based oxypnictide superconductor BaTi$_2$Sb$_2$O

TL;DR

This paper predicts that the layered superconductor BaTi$_2$Sb$_2$O hosts dual topological states, including Dirac semimetal and insulator states, with spin-helical surface states that could enable Majorana modes for quantum computing.

Contribution

It reveals the coexistence of topological Dirac semimetal and insulator states in BaTi$_2$Sb$_2$O, a superconductor, using spectroscopy and calculations, highlighting its potential for topological quantum applications.

Findings

Coexistence of topological Dirac semimetal and insulator states near $E_F$.

Spin-resolved measurements confirm spin-helical surface states.

BaTi$_2$Sb$_2$O hosts dual topological superconducting states.

Abstract

Topological superconductors have long been predicted to host Majorana zero modes which obey non-Abelian statistics and have potential for realizing non-decoherence topological quantum computation. However, material realization of topological superconductors is still a challenge in condensed matter physics. Utilizing high-resolution angle-resolved photoemission spectroscopy and first-principles calculations, we predict and then unveil the coexistence of topological Dirac semimetal and topological insulator states in the vicinity of Fermi energy ($E_F$) in the titanium-based oxypnictide superconductor BaTi$_2$Sb$_2$O. Further spin-resolved measurements confirm its spin-helical surface states around $E_F$, which are topologically protected and give an opportunity for realization of Majorana zero modes and Majorana flat bands in one material. Hosting dual topological superconducting states, the intrinsic superconductor BaTi$_2$Sb$_2$O is expected to be a promising platform for further investigation of topological superconductivity.