Unconventional Quantum Hall Effect and Tunable Spin Hall Effect in monolayer ${\rm MoS_2}$

We analyze the Landau level (LL) structure in a monolayer ${\rm MoS_2}$ and find a field-dependent unconventional quantum Hall plateau sequence $\nu=\cdots$ $-2M-6$, $-2M-4$, $-2M-2$, $-2M-1$, $\cdots$, $-5$, $-3$, $-1$, $0$, $2$, $4$ $\cdots$. Due to orbital asymmetry, the low-energy Dirac fermions become heavily massive and the LL energies grow linearly with $B$, rather than with $\sqrt{B}$. Spin-orbital couplings break spin and valley degenerate LL's into two distinct groups, and LL crossing effects appear in the valence bands only. In a p-n junction, spin-resolved fractionally quantized conductance appears in two-terminal measurements with a controllable spin-polarized current that can be probed at the interface. We also show that the zero-field spin Hall conductivity has some interesting tunability. For more information, please refer to arXiv: 1207.1205.