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(3) thin films creates an emerging topological band structure. Dirac electrons in strained SrNbO(3) films reveal ultrahigh mobility (μ(max) ≈ 100,000 cm(2)/Vs), exceptionally small effective mass (m* ~ 0.04m(e)), and nonzero Berry phase. Strained SrNbO(3) 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(3) 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.