paper

Twisted Boundary Conditions and the Adiabatic Ground State for the Attractive XXZ Luttinger Liquid

arXiv:cond-mat/9206002 · doi:10.1103/PhysRevB.46.14583

Abstract

The one-dimensional attractive lattice fermion gas equivalent to the Heisenberg-Ising spin 1/2 chain is studied for a ring geometry threaded by magnetic flux. We find that for charged fermions having interaction strength with {\it noninteger}, the adiabatic ground state is periodic in the magnetic flux threading the chain, with period 2 flux quanta, as found by Shastry and Sutherland for the repulsive case. We find that, at particular values of the threading field, a sequence of initially zero-energy bound states form at the Fermi surface during the adiabatic process, the largest containing (the integer part of ) fermions. This largest bound state moves around to the other Fermi point and sequentially unbinds. We find Berry's Phase for the whole process to be . For {\it integer}, as increases, eventually all the particles in the system go into bound states of size . The period in this case is of order the size of the system.

24 pages, 10 figures available from authors on request

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