paper

Exact ground state of the sine-square deformed XY spin chain

arXiv:1104.1721 · doi:10.1088/1751-8113/44/25/252001

Abstract

We study the sine-square deformed quantum XY chain with open boundary conditions, in which the interaction strength at the position in the chain of length is proportional to the function . The model can be mapped onto a free spinless fermion model with site-dependent hopping amplitudes and on-site potentials via the Jordan-Wigner transformation. Although the single-particle eigenstates of this system cannot be obtained in closed form, it is shown that the many-body ground state is identical to that of the uniform XY chain with periodic boundary conditions. This proves a conjecture of Hikihara and Nishino [Hikihara T and Nishino T 2011 {\it Phys. Rev. B} \textbf{83} 060414(R)] based on numerical evidence.

10 pages

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