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- Gapless spin liquids in frustrated Heisenberg models

We present our recent numerical calculations for the Heisenberg model on the square and

Kagome lattices, showing that gapless spin liquids may be stabilized in highly-frustrated

regimes. In particular, we start from Gutzwiller-projected fermionic states that may

describe magnetically disordered phases,[1] and apply few Lanczos steps in order to improve

their accuracy. Thanks to the variance extrapolation technique,[2] accurate estimations of

the energies are possible, for both the ground state and few low-energy excitations.

Our approach suggests that magnetically disordered phases can be described by Abrikosov

fermions coupled to gauge fields.

For the Kagome lattice, we find that a gapless U(1) spin liquid with Dirac cones

is competitive with previously proposed gapped spin liquids when only the nearest-neighbor

antiferromagnetic interaction is present.[3,4] The inclusion of a next-nearest-neighbor term

lead to a Z_2 gapped spin liquid,[5] in agreement with density-matrix renormalization group

calculations.[6] In the Heisenberg model on the square lattice with both nearest- and

next-nearest-neighbor interactions, a Z_2 spin liquid with gapless spinon excitations is

stabilized in the frustrated regime.[7] This results are (partially) in agreement with recent

density-matrix renormalization group on large cylinders.[8]

[1] X.-G. Wen, Phys. Rev. B {\bf 44}, 2664 (1991); Phys. Rev. B {\bf 65}, 165113 (2002).

[2] S. Sorella, Phys. Rev. B {\bf 64}, 024512 (2001).

[3] Y. Iqbal, F. Becca, S. Sorella, and D. Poilblanc, Phys. Rev. B 87, 060405(R) (2013).

[4] Y. Iqbal, D. Poilblanc, and F. Becca, Phys. Rev. B 89, 020407(R) (2014).

[5] W.-J. Hu, Y. Iqbal, F. Becca, D. Poilblanc, and D. Sheng, unpublished.

[6] H.-C. Jiang, Z. Wang, and L. Balents, Nat. Phys. 8, 902 (2012);

S. Yan, D. Huse, and S. White, Science 332, 1173 (2011).

[7] W.-J. Hu, F. Becca, A. Parola, and S. Sorella, Phys. Rev. B 88, 060402(R) (2013).

[8] S.-S. Gong, W.Z., D.N. Sheng, O.I. Motrunich, and M.P.A. Fisher, arXiv:1311.5962 (2013).

Collection/Series:

Event Type:

Seminar

Scientific Area(s):

Speaker(s):

Event Date:

Tuesday, May 13, 2014 - 14:00 to 15:30

Location:

Bob Room

©2012 Perimeter Institute for Theoretical Physics