Systematic analysis method for nonlinear response tensors

Understand

We propose a systematic analysis method for identifying essential parameters in various linear and nonlinear response tensors without which they vanish.

• By using the Keldysh formalism and the Chebyshev polynomial expansion method, the response tensors are decomposed into the model-independent and dependent parts, in which the latter is utilized to extract the essential parameters.
• An application of the method is demonstrated by analyzing the nonlinear Hall effect in the ferroelectric SnTe monolayer for example.
• It is shown that in this example the second-neighbor hopping is essential for the nonlinear Hall effect whereas the spin-orbit coupling is unnecessary.