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Pressure-Driven Topological Phase Transition in the Yb Chalcogenides YbO and YbS

By first-principles calculation based on the density functional theory (DFT) with the modified Becke-Johnson local density approximation plus Hubbard U (MBJLDA+U), we studied the band structures of the Yb chalcogenides YbO and YbS under ambient and high pressures. It was revealed that both YbO and YbS have a trivial band topology under ambient pressure, and a nontrivial band topology under high pressure. The topological phase transition is reduced by the pressure-driven single-band inversion between 5d- and 4f -orbitals at the time-reversal invariant momentum (TRIM) point X. A bulk Dirac cone coexisting with a pair of metallic surface states on the [001] surface determined by tight binding model calculation with a slab geometry also demonstrates the nontrivial band topology of YbO and YbS under high pressure.