Theoretical Physics

30 April 2013
Time: 15:00 to 16:00
Location: SR 8.62

Stefanos Kourtis

Topologically and conventionally ordered phases from correlations in flat Chern bands

Several spinless-fermion models featuring topologically non-trivial and
flat bands have been recently studied as a potential host of lattice
fractional quantum-Hall (FQH) states in the absence of a magnetic field,
dubbed fractional Chern insulators (FCI). We introduce such an effective
model on the triangular lattice including short-range interactions,
originally derived from a 3-orbital model describing layered
transition-metal oxides [1,2], and study its ground states as a function
of filling, interaction strength and band dispersion using exact
diagonalization [3]. Using symmetry arguments as well as appropriate
observables, such as the Hall conductivity and the static
charge-structure factor, we identify FCI and charge-density wave (CDW)
ground states at various filling fractions and trace the phase diagram
of the model for some of these fillings. We show that FCI states survive
the competition against CDW states for a wide parameter range and that
they remain robust against disorder in the magnetic background. We also
compare to similar results obtained for a checkerboard-lattice model [4].

[1] J.W.F. Venderbos, M. Daghofer, and J. van den Brink, Phys. Rev.
Lett. 107, 116401 (2011).
[2] J.W.F. Venderbos, S. Kourtis, J. van den Brink, and M. Daghofer,
Phys. Rev. Lett. 108, 126405 (2012).
[3] S. Kourtis, J.W.F. Venderbos, and M. Daghofer, Phys. Rev. B 86,
235118 (2012).
[4] K. Sun, Z. Gu, H. Katsura, and S. Das Sarma, Phys. Rev. Lett. 106,
236803 (2011)



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