Strong tunable photomixing in semi-Dirac materials in the terahertz regime

We demonstrate a strong and anisotropic photomixing effect in an electronic system whose energy–momentum dispersion is parabolic in the 𝑥 direction and linear in the 𝑦 direction, such as a TiO2/VO2 multilayered structure. The third-order photoresponses along the linear and parabolic directions have been analyzed and determined quantitatively. We have found a remarkable tunability of the mixing efficiency along the parabolic direction by a small electric field in the linear direction, up to two orders of magnitude. In the terahertz (THz) regime, the third-order response is comparable to the linear response under an applied field of 103–104  V/cm. Additionally, the nonlinear response persists at room temperature. The results may have applications where different current responses are required along different directions in the THz regime. We demonstrate a strong and anisotropic photomixing effect in an electronic system whose energy–momentum dispersion is parabolic in the 𝑥 direction and linear in the 𝑦 direction, such as a TiO2/VO2 multilayered structure. The third-order photoresponses along the linear and parabolic directions have been analyzed and determined quantitatively. We have found a remarkable tunability of the mixing efficiency along the parabolic direction by a small electric field in the linear direction, up to two orders of magnitude. In the terahertz (THz) regime, the third-order response is comparable to the linear response under an applied field of 103–104  V/cm. Additionally, the nonlinear response persists at room temperature. The results may have applications where different current responses are required along different directions in the THz regime.