It is better to use MEASURE_AVERAGE instead of MEASURE_LOCAL. That way you keep the translation symmetry and the reduction it brings in Hilbert space dimension.
Matthias
On 23 Jun 2010, at 16:43, jun wen wrote:
Hello Matthias,
Thanks for your message. You are right! I found that once I use the graph(where translation symmetry is absent) instead of lattice graph (where translation symmetry is present) to construct the lattice, then the local quantities can be computed via ED.
Best regards, Jun
On Wed, Jun 23, 2010 at 6:55 PM, Matthias Troyer troyer@phys.ethz.ch wrote:
The reason is probably that your lattice is translation invariant - then only average quantities and not local ones are computed, since all local quantities would be the same.
Matthias
On 21 Jun 2010, at 08:33, jun wen wrote:
Hello All,
I was trying to compute the local <S> in the Kitaev model defined on the honeycomb lattice with Exact Diagnolization Here is my parameter file:
MODEL="kitaev"; LATTICE="honeycomb lattice";
LATTICE_LIBRARY="../../../definitions/kitaev/lattices.xml"; MODEL_LIBRARY="../../../definitions/kitaev/models.xml";
MEASURE_LOCAL[Local Sz]=Sz; MEASURE_LOCAL[Local Sx]=Sx; MEASURE_LOCAL[Local Sy]=Sy;
local_S=1/2; L=2; W=2; J=1;
However, in the output xml file, there are no such terms as the Local Sz or Local Splux or Local Sminus. I wonder if anyone could kindly point out what is the problem. The Kitaev model is defined in the following models.xml Thanks a lot!
<MODELS> <SITEBASIS name="spin"> <PARAMETER name="local_spin" default="local_S"/> <PARAMETER name="local_S" default="1/2"/> <QUANTUMNUMBER name="S" min="local_spin" max="local_spin"/> <QUANTUMNUMBER name="Sz" min="-S" max="S"/> <OPERATOR name="Splus" matrixelement="sqrt(S*(S+1)-Sz*(Sz+1))"> <CHANGE quantumnumber="Sz" change="1"/> </OPERATOR> <OPERATOR name="Sminus" matrixelement="sqrt(S*(S+1)-Sz*(Sz-1))"> <CHANGE quantumnumber="Sz" change="-1"/> </OPERATOR> <OPERATOR name="Sz" matrixelement="Sz"/> </SITEBASIS>
<SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR>
<SITEOPERATOR name="Sy" site="x"> 1/2/I*(Splus(x)-Sminus(x)) </SITEOPERATOR>
<BASIS name="spin"> <SITEBASIS ref="spin"/> </BASIS>
<HAMILTONIAN name="kitaev">
<PARAMETER name="J1" default="1"/> <PARAMETER name="Jz" default="J1"/> <PARAMETER name="Jx" default="J1"/> <PARAMETER name="Jy" default="J1"/>
<BASIS ref="spin"/>
<BONDTERM type="0" source="i" target="j"> Jz*Sz(i)*Sz(j) </BONDTERM>
<BONDTERM type="1" source="i" target="j"> Jx*Sx(i)*Sx(j)
</BONDTERM>
<BONDTERM type="2" source="i" target="j"> Jy*Sy(i)*Sy(j)
</BONDTERM> </HAMILTONIAN>
</MODELS>
Jun