Magnetization generation and giant nonlinear transport at symmetry-engineered interfaces

Interfaces in heterostructures possess inherent inversion asymmetry and display diverse physical effects, however, the pristine in-plane mirror symmetries of the constituent layers are usually preserved at the interface. On-demand manipulation of these symmetries remains challenging. Here, we demonstrate a strategy to control the in-plane mirror symmetries of interfaces by engineering the crystallographic orientation of heterostructures. We design a workhorse system with a new orientation, i.e., the LaAlO₃/SrTiO₃ heterostructure with metallic interfaces in the (112)-plane. Such a high index orientation leads to the breaking of all the pristine mirror symmetries except the mirror plane perpendicular to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>[</mml:mo> <mml:mrow><mml:mn>1</mml:mn> <mml:mover><mml:mrow><mml:mn>1</mml:mn></mml:mrow> <mml:mo>¯</mml:mo></mml:mover> <mml:mn>0</mml:mn></mml:mrow> <mml:mo>]</mml:mo></mml:mrow> </mml:math> direction ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mrow><mml:mi>M</mml:mi></mml:mrow> <mml:mrow><mml:mrow><mml:mo>[</mml:mo> <mml:mrow><mml:mn>1</mml:mn> <mml:mover><mml:mrow><mml:mn>1</mml:mn></mml:mrow> <mml:mo>¯</mml:mo></mml:mover> <mml:mn>0</mml:mn></mml:mrow> <mml:mo>]</mml:mo></mml:mrow> </mml:mrow> </mml:msub> </mml:math> ), resulting in the C_s point symmetry with a metallic conduction. Consequently, this interface exhibits a giant nonlinear Hall effect characterized by a large Berry curvature dipole, a circular photogalvanic effect, and current-induced out-of-plane magnetization, all functional at room temperature. The magnitude of the nonlinear Hall effect rivals the Weyl and Dirac systems. Our work establishes a new strategy in exploring emerging electronic properties with nontrivial quantum geometry by designing the interface symmetry.