Evidence of charge transfer in three-dimensional topological insulator/antiferromagnetic Mott insulator Bi1Sb1Te1.5Se1.5/a-RuCl3 heterostructures

We report magnetotransport measurements on Bi1Sb1Te1.5Se1.5/RuCl3 heterostructure nanodevices.Bi1Sb1Te1.5Se1.5 (BSTS) is a strong three-dimensional topological insulator (3D-TI) that hosts conducting topological surface states (TSS) enclosing an insulating bulk. a-RuCl3 (namely, RuCl3) is an antiferromagnet that is predicted to behave as a Kitaev-like quantum spin liquid carrying chargeless Majorana excitations. Temperature (T)-dependent resistivity measurements on BSTS show the interplay between parallel bulk and surface transport channels. For T < 150 K, surface state transport dominates over bulk transport. Multichannel weak antilocalization (WAL) is observed as a sharp cusp in the low-field magnetoconductivity, indicating strong spin-orbit coupling. The presence of top and bottom topological surface states (TSS) including a pair of electrically coupled Rashba surface states (RSS) is indicated. The nonlinear Hall effect, explained by a two-band model, further supports this interpretation. We observed that RuCl3 has an electrostatic effect on the TSS of BSTS, that is, it changes bandbending at the interface as a result of charge transfer. In this regard, the change in low-T logarithmic resistivity upturn in the presence of out-of-plane magnetic field is analyzed employing the Lu-Shen model, supporting the presence of gapless surface states (TSS and RSS) with a p Berry phase.