Correlated oxide Dirac semimetal in the extreme quantum limit.

Quantum materials (QMs) with strong correlation and nontrivial topology are indispensable to next-generation information and computing technologies. Exploitation of topological band structure is an ideal starting point to realize correlated topological QMs. Here, we report that strain-induced symmetry modification in correlated oxide SrNbO thin films creates an emerging topological band structure. Dirac electrons in strained SrNbO films reveal ultrahigh mobility (μ ≈ 100,000 cm/Vs), exceptionally small effective mass (* ~ 0.04), and nonzero Berry phase. Strained SrNbO films reach the extreme quantum limit, exhibiting a sign of fractional occupation of Landau levels and giant mass enhancement. Our results suggest that symmetry-modified SrNbO is a rare example of correlated oxide Dirac semimetals, in which strong correlation of Dirac electrons leads to the realization of a novel correlated topological QM.