Electrically Tunable Circular Photocurrent via Local‐Field Induced Symmetry Breaking at a Metal‐MoTe ₂ Interface

ABSTRACT

The high crystal symmetry of centrosymmetric 2H‐phase transition metal dichalcogenides (TMDCs) inherently forbids the circular photogalvanic effect (CPGE), requiring external stimuli such as electric fields to lower the symmetry for its activation. While Schottky junctions provide a ubiquitous built‐in field, whether such interfaces can generate CPGE in centrosymmetric multilayer 2H‐phase TMDCs and the underlying mechanism remain open questions. In this study, we provide direct electrical evidence of pronounced circular photocurrents in multilayer 2H‐MoTe ₂ under normal incidence by fabricating a localized Au–MoTe ₂ heterostructure. The circular photocurrent exhibits resonant enhancement near the exciton energy of K valleys and is governed by the built‐in electric field, enabling continuous modulation and even sign reversal via an external bias. First‐principles calculations reveal that the Au interface induces a valley‐dependent spin ordering. Crucially, the observation of circular photocurrent under normal incidence corroborates that the in‐plane component of the Schottky built‐in field effectively lowers the C ₃ rotational symmetry of photocurrent generation—a key symmetry requirement for CPGE activation in centrosymmetric systems. These findings elucidate a microscopic mechanism by which a metal–semiconductor interface can activate second‐order or equivalent second‐order CPGE in otherwise forbidden centrosymmetric TMDCs.