Polarization and broken symmetry due to anisotropic "triaxial" strain states in lattice-mismatched quantum wires

Strain states in buried lattice-mismatched quantum wires are studied by polarization analysis with high magnetic fields. Remarkably large in-plane polarization anisotropy is observed, which remains even in very high fields. These results cannot be explained by the isotropic biaxial strain picture, and theoretical calculations show that it is attributed to nonbiaxial (anisotropic triaxial) strain, the symmetry of which is broken. Circular polarization experiments show that Zeeman splitting is highly nonlinear to the field, which is also theoretically explained by the nonbiaxial nature of strain.