Frustration and (111) silicon surface

Overview & Synopsis

Careful analysis of the currently available experimental data on (111) surface of silicon leads us to believe that a positive correlation energy and positive dispersion are responsible for a split surface band of dangling electrons. The resultant ground-state is paramagnetic and insulating but cannot order antiferromagnetically because of the pathological frustration of the triangular lattice. Instead a ground-state results of two correlated zig-zag Heisenberg chains of S = 1/2 electrons for the unconstructed (1×1) surface. Surface reconstruction lifts the degeneracy between the two chains, stabilizes the well-known (2×1) surface and gives it a pronounced one-dimensional character.