Topological superconductivity from ferroelectric fluctuations

A topological superconductor features at its boundary Majorana fermions, which are potentially applicable for topological quantum computations. Research on the topological superconductivity has been hampered by the scarcity of the real systems. Therefore, there is a strong demand for such an unconventional superconductivity. In this research, we study a heterostructure consisting of a two-dimensional electron gas (2DEG) from 5d transition metals sandwiched by ferroelectric materials using first-principle DFT calculations. This system possesses suitable conditions for the topological superconductivity: it has a strong spin-orbit coupling, and with odd-parity phonon modes at low energy due to ferroelectric fluctuations. The band structure calculations show the Rashba type spin splitting, which results from the spin-orbit coupling and inversion symmetry breaking. Setting the substrate lattice constant at an appropriate range softens the odd-parity phonon mode to induce the strong electron-phonon coupling. Our results indicate that appropriately strained substrates with an extremely soft phonon mode may give rise to the topological superconductivity on 2DEG. We will suggest several candidate substrates and experimental probing techniques.