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R2917/StagFluxTransExciton.cpp
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StagFluxTransExciton.cpp
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#include <set>
#include "StagFluxTransExciton.h"
#include "linalg.h"
using namespace std;
StagFluxTransExciton::StagFluxTransExciton(size_t Lx,
size_t Ly,
double phi,
double neel,
double *bc_phase,
size_t *q,
double Ecutoff)
:StagFluxWaveFunction(Lx,Ly,
Lx*Ly/2+1,Lx*Ly/2-1,
phi,neel,bc_phase)
{
m_q[0]=q[0];
m_q[1]=q[1];
vector<double> en(Lx*Ly/2,0);
// add all two-spinons excitons
for(size_t fe=0;fe<Lx*Ly/2;++fe){
size_t kx=m_fock2qn[3*(2*fe+1)];
size_t ky=m_fock2qn[3*(2*fe+1)+1];
double k[2]={double(kx)*2*M_PI/Lx,double(ky)*2*M_PI/Ly};
en[fe]=omega(k);
size_t Qk[2]={linalg::mod(int(kx)-int(m_q[0]),m_Lx),
linalg::mod(int(ky)-int(m_q[1]),m_Ly)};
mbzmod(Qk);
vector<size_t> stup(Lx*Ly,Lx*Ly/2+1);
vector<size_t> stdo(Lx*Ly,Lx*Ly/2-1);
size_t do_count(0);
for(size_t f=0;f<(Lx*Ly)/2;++f){
stup[2*f]=f;
if(m_qn2fock[(Qk[0]*Ly+Qk[1])*2]!=2*f){
stdo[2*f]=do_count;
++do_count;
}
}
stup[2*fe+1]=Lx*Ly/2;
add_state(&stup[0],&stdo[0]);
}
// add four-spinons excitons such that the mean-field energy of
// the excitation is less than Ecutoff
set<string> pickedstates;
for(size_t fe1=0;fe1<Lx*Ly/2;++fe1){
size_t k1[2]={m_fock2qn[3*(2*fe1+1)],m_fock2qn[3*(2*fe1+1)+1]};
for(size_t fe2=0;fe2<Lx*Ly/2;++fe2){
size_t k2[2]={m_fock2qn[3*(2*fe2+1)],m_fock2qn[3*(2*fe2+1)+1]};
for(size_t fe3=0;fe3<Lx*Ly/2;++fe3){
size_t k3[2]={m_fock2qn[3*(2*fe3+1)],m_fock2qn[3*(2*fe3+1)+1]};
size_t k4[2]={linalg::mod(int(k1[0])+int(k3[0])-int(k2[0])-int(m_q[0]),m_Lx),
linalg::mod(int(k1[1])+int(k3[1])-int(k2[1])-int(m_q[1]),m_Ly)};
mbzmod(k4);
size_t fe4=Lx*Ly/2;
for(size_t f=0;f<Lx*Ly/2;++f){
if(m_fock2qn[3*(2*f+1)]==k4[0] && m_fock2qn[3*(2*f+1)+1]==k4[1]){
fe4=f;
}
}
if(fe4==Lx*Ly/2){
throw(std::logic_error("Excited state k4=k1+k3-k2-q could not be found. This is a bug."));
}
// calculate Delta-E. Energies associated to fe2 and fe4 are negative thus the simple sum below.
double DE=en[fe1]+en[fe3]+en[fe2]+en[fe4];
if(DE<Ecutoff){
for(size_t sig=0;sig<2;++sig){
// remove when either creating twice same state or destroying twice.
if((sig && (fe2==fe4)) || (!sig && (fe1==fe3))) continue;
size_t up_count=0;
size_t do_count=0;
vector<size_t> stup(Lx*Ly,Lx*Ly/2+1);
vector<size_t> stdo(Lx*Ly,Lx*Ly/2-1);
// create fock state, populating the bottom band first.
for(size_t f=0;f<Lx*Ly/2;++f){
if(sig){
stup[2*f]=up_count;
++up_count;
if(f!=fe2 && f!=fe4){
stdo[2*f]=do_count;
++do_count;
}
} else {
if(f!=fe4){
stup[2*f]=up_count;
++up_count;
}
if(f!=fe2){
stdo[2*f]=do_count;
++do_count;
}
}
}
// add the top band particles
if(sig){
stup[2*fe1+1]=up_count;
stdo[2*fe3+1]=do_count;
} else {
stup[2*fe3+1]=up_count;
stup[2*fe1+1]=up_count+1;
}
string strup,strdo;
fock2str(stup,strup,Lx*Ly/2+1);
fock2str(stdo,strdo,Lx*Ly/2-1);
if(pickedstates.find(strup+strdo)==pickedstates.end()){
add_state(&stup[0],&stdo[0]);
pickedstates.insert(strup+strdo);
}
}
}
}
}
}
}
void StagFluxTransExciton::fock2str(const vector<size_t>& fo, string& str, size_t Nfs)
{
str.resize(fo.size());
for(size_t n=0;n<fo.size();++n){
if(fo[n]==Nfs) str[n]='e';
else str[n]='0';
}
}
StagFluxTransExciton::~StagFluxTransExciton()
{}
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