Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 47: Correlated Electrons: Spin Systems and Itinerant Magnets 2
TT 47.8: Vortrag
Freitag, 30. März 2012, 11:30–11:45, H 0104
Emergent critical phase in 2D frustrated Heisenberg model — •Peter Philipp Orth1, Premala Chandra2, Piers Coleman2, and Jörg Schmalian1 — 1Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany — 2Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
It is well-known that a discrete Ising (Z2) order parameter emerges in the frustrated square lattice J1-J2-Heisenberg model, which may be broken at finite temperature. We ask whether a different discrete symmetry Zq with q>2 may be found in other frustrated Heisenberg models, giving rise to a different finite temperature phase transition. Indeed, we identify an emergent Z6 symmetry at low temperatures in a frustrated Heisenberg model on a 2D lattice that contains both the sites of the triangular and its dual honeycomb lattice. Our analysis combines a spin-wave expansion, susceptible to short-distance physics, with renormalization group arguments of the corresponding long-wavelength non-linear sigma model. Our results are even more appealing since the Z6 clock model has a rich finite temperature phase diagram with two distinct Berezinskii-Kosterlitz-Thouless (BKT) phase transitions separated by a massless critical phase. We also discuss possible realizations of this system using cold-atoms in optical lattices.