In2AB Janus Double-Layered Honeycomb Structures with Nontrivial Topology and Rashba Splitting (A, B = P, As, Sb, or Bi)

Two-dimensional (2D) systems serve as promising platforms for engineering nanoscale devices and for exploring emergent quantum phenomena. The recent experimental realization of AlSb in a double-layer honeycomb (DLHC) configuration confirms the prior theoretical predictions that traditional semiconductors are stable in DLHC configurations at the ultrathin limit and paves the way for systematic exploration of structurally robust DLHC materials. In this work, we have studied In-based InA (A = P, As, Sb, or Bi) in wurtzite, zincblende, DLHC, and AA configurations and found that all the pristine InA structures energetically prefer the DLHC structure. The Z₂ topological invariant number calculation showed that the pristine case is topologically trivial. Furthermore, using the energetically favored configuration, we tailored a Janus In₂AB (A and B = P, As, Sb, or Bi) that breaks the inversion symmetry. Topological property calculations under the hybrid HSE06 functional reveal that three out of six compounds (In₂PSb, In₂AsSb, and In₂BiSb) exhibit nontrivial topology with system band gaps of 527, 456, and 649 meV, respectively. The presence of gapless edge states further confirmed the nontrivial topological property of these compounds. Moreover, In₂PSb also showed a significant isotropic Rashba splitting, with a Rashba parameter of α_R = 1.45 eV Å. These materials with nontrivial topology and Rashba-like splitting might have meaningful applications in spintronics.