Topological-Metal to Band-Insulator Transition in (Bi1-xInx)2Se3 Thin Films

By combining transport and photoemission measurements on (Bi_1-xIn_x)₂Se₃ thin films, we report that this system transforms from a topologically nontrivial metal into a topologically trivial band insulator through three quantum phase transitions. At x≈3%-7%, there is a transition from a topologically nontrivial metal to a trivial metal. At x≈15%, the metal becomes a variable-range-hopping insulator. Finally, above x≈25%, the system becomes a true band insulator with its resistance immeasurably large even at room temperature. This material provides a new venue to investigate topologically tunable physics and devices with seamless gating or tunneling insulators.