Enhanced stability and superconductivity of IrTe2/In2Se3 heterobilayers with ferroelectrically switchable band topology

Recent advances in realizing ferroelectric and superconducting two-dimensional heterobilayers provide appealing platforms for exploring the interplay between ferroelectricity and superconductivity, which is not only crucial for understanding the superconducting mechanism but also important for designing next-generation superconducting devices. Based on first-principles calculations, we demonstrate that an ${\mathrm{IrTe}}_{2}$ monolayer can be stabilized on a ferroelectric ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ monolayer via interlayer coupling. The superconducting transition temperature of the ${\mathrm{IrTe}}_{2}/{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ heterobilayer is substantially enhanced from that of bulk ${\mathrm{IrTe}}_{2}$ mainly due to enhanced interlayer coupling, supplemented by the increase in the density of states at the Fermi level and phonon softening; the latter is further tied to Fermi surface nesting. Our calculations show that superconductivity is dominant over several typical competing orders, including charge density wave, magnetism, and nematicity. Moreover, we find that the band topology of ${\mathrm{IrTe}}_{2}/{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ can be switched between trivial and nontrivial by reversing the ferroelectric polarization of the ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ substrate. By further substituting Ir with Pd, the topological edge states can be tuned close to the Fermi level, making ${\mathrm{IrTe}}_{2}/{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ a potential candidate for realizing topological superconductivity. Our work provides a realistic system that can simultaneously harbor ferroelectricity, superconductivity, and nontrivial band topology, paving the way for integrating multiple applications, such as superconducting field transistors, topological quantum computing, and tunable superconducting diodes, in a single system.