Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 1 (jointly with MA)
TT 5.10: Vortrag
Montag, 16. März 2015, 12:00–12:15, H 0110
Emergent critical phase and Z6 order in the windmill lattice antiferromagnet — •Peter P Orth1, Bhilahari Jeevanesan1, Joerg Schmalian1, Premala Chandra2, and Piers Coleman2 — 11Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany — 2Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
In most systems that exhibit order at low temperatures, the order occurs in the elementary degrees of freedom such as spin or charge. Prominent examples are magnetic or superconducting states of matter. In contrast, emergent order describes the phenomenon where composite objects exhibit longer range correlations. Such emergent order has been suspected to occur in a range of correlated materials. One specific example are spin systems with competing interactions, where long-range discrete order in the relative orientation of spins may occur.
One example is the recently introduced two-dimensional antiferromagnet on the windmill lattice that shows an emergent Z6 symmetry. The rich ground state phase diagram exhibits intricate spiral and non-coplanar phases. At finite temperature, order by disorder leads to a decoupling of an emergent collective degree of freedom given by the relative phase of spins on different sublattices. Using large scale classical parallel tempering Monte Carlo simulations, we present numerical evidence that the emergent order parameter undergoes a sequence of two Berezinskii-Kosterlitz-Thouless phase transitions that bracket a critical phase. We discuss extensions of this model and physical realizations.