Superconductivity Bordering Rashba Type Topological Transition

Correlated oxide Dirac semimetal in the extreme quantum limit

Quantum materials (QMs) with strong correlation and nontrivial topology are indispensable to next-generation information and computing technologies. Exploitation of topological band structure is an ideal starting point to realize correlated topological QMs. Here, we report that strain-induced symmetry modification in correlated oxide SrNbO₃ thin films creates an emerging topological band structure. Dirac electrons in strained SrNbO₃ films reveal ultrahigh mobility (μ_max ≈ 100,000 cm²/Vs), exceptionally small effective mass (m* ~ 0.04m_e), and nonzero Berry phase. Strained SrNbO₃ films reach the extreme quantum limit, exhibiting a sign of fractional occupation of Landau levels and giant mass enhancement. Our results suggest that symmetry-modified SrNbO₃ is a rare example of correlated oxide Dirac semimetals, in which strong correlation of Dirac electrons leads to the realization of a novel correlated topological QM.

Electrically Controlled Spin Injection from Giant Rashba Spin-Orbit Conductor BiTeBr

Ferromagnetic materials are the widely used source of spin-polarized electrons in spintronic devices, which are controlled by external magnetic fields or spin-transfer torque methods. However, with increasing demand for smaller and faster spintronic components utilization of spin-orbit phenomena provides promising alternatives. New materials with unique spin textures are highly desirable since all-electric creation and control of spin polarization is expected where the strength, as well as an arbitrary orientation of the polarization, can be defined without the use of a magnetic field. In this work, we use a novel spin-orbit crystal BiTeBr for this purpose. Because of its giant Rashba spin splitting, bulk spin polarization is created at room temperature by an electric current. Integrating BiTeBr crystal into graphene-based spin valve devices, we demonstrate for the first time that it acts as a current-controlled spin injector, opening new avenues for future spintronic applications in integrated circuits.

Fermi level tuning of Ag-doped Bi2Se3 topological insulator

The temperature dependence of the resistivity (ρ) of Ag-doped Bi₂Se₃ (Ag_xBi_2−xSe₃) shows insulating behavior above 35 K, but below 35 K, ρ suddenly decreases with decreasing temperature, in contrast to the metallic behavior for non-doped Bi₂Se₃ at 1.5–300 K. This significant change in transport properties from metallic behavior clearly shows that the Ag doping of Bi₂Se₃ can effectively tune the Fermi level downward. The Hall effect measurement shows that carrier is still electron in Ag_xBi_2−xSe₃ and the electron density changes with temperature to reasonably explain the transport properties. Furthermore, the positive gating of Ag_xBi_2−xSe₃ provides metallic behavior that is similar to that of non-doped Bi₂Se₃, indicating a successful upward tuning of the Fermi level.