We propose a simple and general semi-analytical method, based on the effective mass approximation, for determining the ground state of a cluster of two donors. The method can be employed for an arbitrary orientation of the cluster axis and is especially useful for revealing the valley composition of the ground state. It can be generalised to calculate (i) the exchange between two sets of donor clusters where the axis of each cluster and their relative orientation may differ (ii) the strength of the hyperfine interaction and its interplay with an external electric field. Numerical results can be benchmarked against more advanced tight-binding techniques. I will discuss the ground state of donor clusters along the (100), (110) and (111) directions as well as preliminary results for inter-cluster exchange, with a particular focus on suppressing valley oscillations in the latter [1].

References
[1] B. Koiller, X. Hu, and S. Das Sarma, Phys. Rev. Lett. 88, 027903 (2002).

Dimitrie Culcer obtained his PhD from the University of Texas at Austin in 2005. He worked as a postdoctoral research fellow first at Argonne National Laboratory between 2006-2008, and subsequently at the University of Maryland, College Park, 2008-2010. He became a faculty member at the University of Science and Technology of China in Hefei in 2010, where he was a member of the International Center for Quantum Design of Functional Materials. In 2013 he moved to the School of Physics, University of New South Wales in Sydney. Dimitrie Culcer’s research interests include quantum information and computation, spin-orbit coupling and topological effects in condensed matter physics, quantum transport theory and electron-electron interaction effects, in particular the interplay of interactions with strong spin-orbit coupling. He is actively working in all these areas.