Topological phase transition in a single material usually refers totransitions between a trivial band insulator and a topological Dirac phase, butthe transition may also occur between different classes of topological Diracphases. However, it is a fundamental challenge to realize quantum transitionbetween Z2 nontrivial topological insulator (TI) and topological crystallineinsulator (TCI) in one material because Z2 TI and TCI are hardly both co-existin a single material due to their contradictory requirement on the number ofband inversions. The Z2 TIs must have an odd number of band inversions over allthe time-reversal invariant momenta, whereas, the newly discovered TCIs, as adistinct class of the topological Dirac materials protected by the underlyingcrystalline symmetry, owns an even number of band inversions. Here, takePbSnTe2 alloy as an example, we show that at proper alloy composition theatomic-ordering is an effective way to tune the symmetry of the alloy so thatwe can electrically switch between TCI phase and Z2 TI phase when the alloy isordered from a random phase into a stable CuPt phase. Our results suggest thatatomic-ordering provides a new platform to switch between different topologicalphases.
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