Volume 79, Number 3, August 2007
Article Number 37001
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 16 July 2007
EPL, 79 (2007) 37001
DOI: 10.1209/0295-5075/79/37001

Entanglement entropy of aperiodic quantum spin chains

F. Iglói1, 2, R. Juhász1 and Z. Zimborás3

1  Research Institute for Solid State Physics and Optics - H-1525 Budapest, P.O. Box 49, Hungary
2  Institute of Theoretical Physics, Szeged University - H-6720 Szeged, Hungary
3  Research Institute for Particle and Nuclear Physics - H-1525 Budapest, P.O. Box 49, Hungary

received 3 April 2007; accepted in final form 18 June 2007; published August 2007
published online 16 July 2007

We study the entanglement entropy of blocks of contiguous spins in non-periodic (quasi-periodic or more generally aperiodic) critical Heisenberg, XX and quantum Ising spin chains, e.g. in Fibonacci chains. For marginal and relevant aperiodic modulations, the entanglement entropy is found to be a logarithmic function of the block size with log-periodic oscillations. The effective central charge, $c_{{\rm eff}}$, defined through the constant in front of the logarithm may depend on the ratio of couplings and can even exceed the corresponding value in the homogeneous system. In the strong modulation limit, the ground state is constructed by a renormalization group method and the limiting value of $c_{{\rm eff}}$ is exactly calculated. Keeping the ratio of the block size and the system size constant, the entanglement entropy exhibits a scaling property, however, the corresponding scaling function may be nonanalytic.

75.10.Jm - Quantized spin models.
03.65.Ud - Entanglement and quantum nonlocality.
75.50.Kj - Amorphous and quasicrystalline magnetic materials.

© Europhysics Letters Association 2007