Possible new bubble phases of two-dimensional electrons in higher Landau   levels
  We argue that, due to the specific form of the interaction potential between electronic guiding centers, a bubble crystal (BC) with basis may be energetically more favorable than the usual bubble solid. This new BC has well-defined normal eigenmodes, and remains energetically favorable when the effects of finite sample thickness and of screening by electrons in lower LLs are taken into account. 
A.M. Ettouhami, F.D. Klironomos and A.T. Dorsey