Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session M15: Focus Session: Spin/orbital Frustration and Short-range Order
8:00 AM–11:00 AM,
Wednesday, March 20, 2013
Sponsoring Units: GMAG DMP
Chair: Collin Broholm, Johns Hopkins University
Abstract ID: BAPS.2013.MAR.M15.1
Abstract: M15.00001 : Spin-orbital quantum liquid on the honeycomb lattice*
8:00 AM–8:36 AM
Preview Abstract Abstract
(Theoretische Physik, ETH Zurich, Switzerland)
The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. This approach can be seen as a two-dimensional generalization of matrix product states - the underlying ansatz of the density matrix renormalization group method. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-N\'eel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a good starting point to understand the recently discovered spin-orbital liquid behavior of Ba$_3$CuSb$_2$O$_9$. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms.
*We acknowledge the financial support from the Swiss National Science Foundation.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.M15.1
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