Re: [ALPS-users] the right way to define a harmonic trap

15 Mar 2013

      Hi,

The harmonic trap which I used in (the ALPS part of) the calculation of
PRB82, 014202 (2010) (http://dx.doi.org/10.1103/PhysRevB.82.014202) are:

1. define "inhomogeneous chain lattice" as follows:

<LATTICEGRAPH name = "inhomogeneous open chain lattice">
  <FINITELATTICE>
    <LATTICE ref="chain lattice"/>
    <EXTENT dimension="1" size ="L"/>
    <BOUNDARY type="open"/>
  </FINITELATTICE>
  <UNITCELL ref="simple1d"/>
  <INHOMOGENEOUS><VERTEX/></INHOMOGENEOUS>
</LATTICEGRAPH>

2. add site-dependent 'mu' term in the parameter file:

LATTICE="inhomogeneous open chain lattice"
MODEL="fermion Hubbard"
CONSERVED_QUANTUMNUMBERS="Nup,Ndown"
L=20
t=1
U=2
mu=-0.006*(x-L/2+0.5)^2
{ Nup_total=10; Ndown_total=10 }

At least the above setting works fine for ALPS DMRG code.
Of course you should check the convergence carefully by changing sweeps.

I don't think changing the model is necessary.

Best regards,
--
Ryo IGARASHI, Ph.D.
rigarash@issp.u-tokyo.ac.jp
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