Abstract
We study the effect of mass anisotropy on the magnetic ordering of the Wigner crystal phase of low density electron systems in two dimensions at T = 0. We apply the instanton approximation to various ring exchange processes, which includes the lowest order Gaussian fluctuations beyond the WKB approximation. The multi-particle exchange frequencies are calculated with effective mass anisotropy, both with and without ensuing lattice distortions. We find that when sufficient mass anisotropy is present, the two-spin exchange process between the nearest neighbors becomes more frequent than the three particle processes. Therefore, its corresponding antiferromagnetic exchange exceeds the ferromagnetic exchange from the three-spin process and becomes dominant. Numerical diagonalization of small clusters with two, three, and four-spin exchange terms shows a transition from a ferromagnetic to an antiferromagnetic ground state with increasing mass anisotropy.
Original language | English (US) |
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Pages (from-to) | 1547-1549 |
Number of pages | 3 |
Journal | Physica B: Condensed Matter |
Volume | 403 |
Issue number | 5-9 |
DOIs | |
State | Published - Apr 1 2008 |
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
Keywords
- Mass anisotropy
- Ring exchange
- Two-dimensional electron system
- Wigner crystal