Decoupling Surface and Bulk States via Third-Order Electrical Nonlinearity in Centrosymmetric Crystal

Area of Science:

• Condensed matter physics
• Materials science
• Semiconductor physics

Background:

• Surface states are critical for semiconductor and topological physics but are often obscured by bulk contributions.
• Complex surface-bulk coupling and symmetry-breaking hinder the isolation and study of these surface states.

Purpose of the Study:

• To overcome the challenge of distinguishing surface electronic properties from bulk contributions in centrosymmetric materials.
• To develop a novel method for characterizing surface states and their discrepancies with bulk electronic structures.

Main Methods:

• Utilizing dual-axes third-order nonlinear transport measurements in centrosymmetric ZrTe5.
• Exploiting symmetry constraints to achieve directional separation of surface- and bulk-dominated responses.
• Employing isotropic surface modification to induce anisotropic nonlinear transport modulation.

Main Results:

• Achieved distinct directional propagation for surface and bulk responses, enabling effective state decoupling.
• Demonstrated giant third-order conductivities exceeding 10^4 μm Ω^-1 V^-2.
• Showcased robust performance of the method up to 300 K, highlighting its broad operational window.

Conclusions:

• The developed strategy effectively decouples surface and bulk states in centrosymmetric systems by relaxing crystalline symmetry constraints.
• This approach provides a low-frequency, nondestructive electrical probe for resolving electronic structure evolution discrepancies between surfaces and bulk.
• Offers a new pathway for characterizing quantum geometry and Lifshitz transitions at surfaces, distinct from conventional nonlinear optical methods.