Effect of an Interface step on Tunnel Coupling and Energy Spectrum in a Si/SiGe double quantum dot

Understanding the effect of a rough interface on valley-orbit coupling in Si quantum dots is crucial in determining its suitability for application in quantum information processing. Interface roughness, such as an atomic step at the interface of Si and SiGe alloy leads to a change in the magnitude and phase of the valley-orbit coupling in a single quantum dot. Here we study the effect of interface steps on the spectrum and particularly tunnel coupling in a double quantum dot. More specifically, we explore how inter-valley tunneling depends on the location and orientation of the step(s). We also investigate the interplay between a magnetic field and an interface step, and how it affects the state of an electron. Our results show that the geometry of a step is an important factor in determining the energy spectrum and tunneling coupling of a single electron in a Si double quantum dot.