Ferroelectric Rashba topological phase in noncentrosymmetric CsSiBi

Composite quantum compounds (CQCs) provide a platform to explore the mutual interplay between seemingly independent physical phenomena, providing new insights into their coupled behavior. In particular, the giant Rashba effect, ferroelectric switching and non-trivial band topology represent symmetry-driven, local and global characteristics of materials, respectively, thereby offering both novel functionalities and deeper insight into fundamental physics. In present work, we investigated CsSiBi and CsPbSb compounds for potential CQCs within<i>first-principles</i>calculations using Vienna ab-initio simulation package and WIEN2k with symmetry analysis. The stability of both compounds is systematically examined by evaluating their chemical, mechanical, dynamical and thermal characteristics. The CsSiBi coined as intrinsic CQC with topological insulating phase, Rashba spin-splitting and ferroelectric switching while CsPbSb limited to very large isotropic Rashba effect. The spin-texture reversal, large polarization and ferroelectric double well energy profile validate the ferroelectricity and facilitates the electrical manipulation for spin degrees of freedom in new CQC CsSiBi. The calculated values ofαRΓ-MandαRΓ-Kfor CsSiBi (CsPbSb) are 2.46 eV Å (5.71 eV Å) and 2.47 eV Å (5.71 eV Å), respectively which indicates giant<i>isotropic</i>Rashba effect. Our study also validates the recent reports on enhanced reliability of full-potential codes in analyzing electronic band structure of materials exhibiting surface-induced asymmetry. The confluence of aforementioned properties open avenues for more reliable next-generation multifunctional materials for spintronics and nanoelectronics.