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

Surface states, crucial electronic properties in semiconductors and topological physics, are conventionally overwhelmed from bulk contributions due to complex surface-bulk coupling and symmetry-breaking constraints. Here, we overcome this obstacle by dual-axes third-order nonlinear transports in centrosymmetric ZrTe₅, where surface and bulk dominated responses propagate along distinct directions, respectively. This pronounced state separation arising from specific symmetry constraints results in anisotropic nonlinear transport modulation via isotropic surface modification, enabling an application of accurate characterization to mismatched Lifshitz transitions and quantum geometry between surface and bulk. Meanwhile, the state decoupling approach offers a broad operational window, producing giant third-order conductivities >10⁴ μm Ω ^-1 V^-2 and robust performance up to 300 K. Our strategy relaxes crystalline symmetry constraints to centrosymmetric systems for effective surface-bulk decoupling, and provides a low-frequency, nondestructive electrical probe for resolving evolution discrepancies between fine electronic structures of surface and bulk, distinguished from conventional nonlinear optics.