Valley-orbit coupling is a key parameter for a silicon quantum dot in determining its suitability for applications in quantum information processing. In this paper we study the effect of interface steps on the magnitude and phase of valley-orbit coupling for an electron in a silicon quantum dot. Within the effective mass approximation, we find that the location of a step on the interface is important in determining both the magnitude and the phase of the valley-orbit coupling in a Si/SiGe quantum dot. Specifically, our numerical results show that the magnitude of valley orbit coupling can be suppressed up to 75% by a step of one atomic monolayer, and its phase can change by almost π. When two steps are present, the minimum value of the valley-orbit coupling can even approach zero. We also clarify the effects of an applied external magnetic field and the higher orbital states on the valley-orbit coupling. Overall, our results illustrate how interface roughness affect the valley-orbit coupling in silicon, and how spin qubits in silicon may be affected.PACS numbers:

Since last decade corporate sustainability has been of great interest to practitioners and researchers, both. Successful implementation of sustainability practices is vital for organizational survival and competitive advantage. Based on institutional theory, this study aims at to enhance understanding regarding the relationship of sustainability practices and corporate performance directly and indirectly through non-financial performance. Data from managerial level employees of manufacturing and services providing organizations of Pakistan was collected through a survey questionnaire. Based on 346 participants’ responses we found that sustainability practices (exploration and exploitation) have significant relationship with financial and market performance. The multi-mediation analysis shows that all mediators partially mediate the relationship between sustainability practices and corporate performance. In the context of Pakistan, this study is the first of its kind to validate sustainability practices scale.

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The mixing of conduction band valleys plays a critical role in determining electronic spectrum and dynamics in a silicon nanostructure. Here, we investigate theoretically how valley–orbit coupling affects the exchange interaction in a silicon double quantum dot. We find that exchange splitting can be strongly suppressed at finite valley phase differences between the dots because of the valley-phase-dependent dressing of the ground states and Coulomb exchange integrals, and a small valley splitting can render the exchange Hamiltonian incomplete in describing low-energy dynamics due to nearby excited valley states. The higher orbital states are also vital in calculating the exchange splitting, which is crucial for applications such as exchange gates for spin qubits.