Topological Phase Transition from a Quantum Spin Hall Insulator to a Chern Insulator*

The effect of magnetic field on electronic transport in InAs/GaSb quantum spin Hall systems is investigated. As theoretical works [1-3] indicate, the system will undergo an insulator-metal-insulator phase transition at a critical magnetic field where the lowest Landau Levels (LLs) of electron and hole cross. Here we observe a distinct bulk conductance peak emerging around 12T in InAs/GaSb double layer systems. Both its temperature dependence and abruptly increasing signal fluctuation is consistent with a metallic phase arising from the topological phase transition between a QSHI phase and a Chern insulator phase. In the meanwhile the response of helical edge state is also systematically studied and the results will be presented.

[1] D. Pikulin, T. Hyart, S. Mi et al., Phy. Rev. B 89, 161403 (R) (2014)
[2] S. Zhang, Y. Zhang and S. Shen, Phy. Rev. B 90, 115305 (2014)
[3] J. Chen, J. Wang and Q. Shun, Phy. Rev. B 85, 125401 (2012)