HubbardSU2.h

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#ifndef HUBBARDMODELSU2_H_
#define HUBBARDMODELSU2_H_
 
#include "models/HubbardSU2xU1.h"
#include "symmetry/SU2.h"
#include "bases/FermionBase.h"
#include "models/HubbardObservables.h"
//include "tensors/SiteOperatorQ.h"
//include "tensors/SiteOperator.h"
#include "Mpo.h"
//include "DmrgExternal.h"
//include "ParamHandler.h"
#include "ParamReturner.h"
#include "Geometry2D.h" // from TOOLS
 
namespace VMPS
{
 
class HubbardSU2 : public Mpo<Sym::SU2<Sym::SpinSU2> ,double>,
                   public HubbardObservables<Sym::SU2<Sym::SpinSU2> >,
                   public ParamReturner
{
public:
    
    typedef Sym::SU2<Sym::SpinSU2> Symmetry;
    MAKE_TYPEDEFS(HubbardSU2)
    typedef Eigen::Matrix<double,Eigen::Dynamic,Eigen::Dynamic> MatrixType;
    typedef SiteOperatorQ<Symmetry,MatrixType> OperatorType;
    
private:
    
    typedef Eigen::Index Index;
    typedef Symmetry::qType qType;
    
public:
    
    HubbardSU2() : Mpo(){};
    
    HubbardSU2(Mpo<Symmetry> &Mpo_input, const vector<Param> &params)
    :Mpo<Symmetry>(Mpo_input),
     HubbardObservables(this->N_sites,params,HubbardSU2::defaults),
     ParamReturner(HubbardSU2::sweep_defaults)
    {
        ParamHandler P(params,HubbardSU2::defaults);
        size_t Lcell = P.size();
        N_phys = 0;
        for (size_t l=0; l<N_sites; ++l) N_phys += P.get<size_t>("Ly",l%Lcell);
        this->precalc_TwoSiteData();
        this->HERMITIAN = true;
        this->HAMILTONIAN = true;
    };
    
    HubbardSU2 (const size_t &L, const vector<Param> &params, const BC &boundary=BC::OPEN, const DMRG::VERBOSITY::OPTION &VERB=DMRG::VERBOSITY::OPTION::ON_EXIT);
    
    static void add_operators (const std::vector<FermionBase<Symmetry> > &F, const ParamHandler &P, PushType<SiteOperator<Symmetry,double>,double>& pushlist,
                               std::vector<std::vector<std::string>>& labellist, const BC boundary=BC::OPEN);
    
    static qarray<1> singlet (int N=0) {return qarray<1>{1};};
    static constexpr MODEL_FAMILY FAMILY = HUBBARD;
    static constexpr int spinfac = 1;
    
    static const map<string,any> defaults;
    static const map<string,any> sweep_defaults;
};
 
// V is standard next-nearest neighbour density interaction
// Vz and Vxy are anisotropic isospin-isospin next-nearest neighbour interaction
const map<string,any> HubbardSU2::defaults = 
{
    {"t",1.}, {"tPrime",0.}, {"tRung",1.}, {"tPrimePrime",0.},
    {"mu",0.}, {"t0",0.}, 
    {"U",0.}, {"Uph",0.},
    {"V",0.}, {"Vext",0.}, {"Vrung",0.},
    {"Vz",0.}, {"Vzrung",0.}, {"Vxy",0.}, {"Vxyrung",0.}, 
    {"J",0.}, {"Jperp",0.},
    {"X",0.}, {"Xrung",0.},
    {"REMOVE_DOUBLE",false}, {"REMOVE_EMPTY",false}, {"REMOVE_UP",false}, {"REMOVE_DN",false}, {"mfactor",1}, {"k",0}, 
    {"maxPower",2ul}, {"CYLINDER",false}, {"Ly",1ul}
};
 
const map<string,any> HubbardSU2::sweep_defaults = 
{
    {"max_alpha",100.}, {"min_alpha",1.}, {"lim_alpha",11ul}, {"eps_svd",1e-7},
    {"Dincr_abs", 4ul}, {"Dincr_per", 2ul}, {"Dincr_rel", 1.1},
    {"min_Nsv",0ul}, {"max_Nrich",-1},
    {"max_halfsweeps",24ul}, {"min_halfsweeps",6ul},
    {"Minit",1ul}, {"Qinit",1ul}, {"Mlimit",500ul},
    {"tol_eigval",1e-7}, {"tol_state",1e-6},
    {"savePeriod",0ul}, {"CALC_S_ON_EXIT", true}, {"CONVTEST", DMRG::CONVTEST::VAR_2SITE}
};
 
HubbardSU2::
HubbardSU2 (const size_t &L, const vector<Param> &params, const BC &boundary, const DMRG::VERBOSITY::OPTION &VERB)
:Mpo<Symmetry> (L, qarray<Symmetry::Nq>({1}), "", PROP::HERMITIAN, PROP::NON_UNITARY, boundary, VERB),
 HubbardObservables(L,params,HubbardSU2::defaults),
 ParamReturner(HubbardSU2::sweep_defaults)
{
    ParamHandler P(params,defaults);
    size_t Lcell = P.size();
    
    for (size_t l=0; l<N_sites; ++l)
    {
        N_phys += P.get<size_t>("Ly",l%Lcell);
        setLocBasis(F[l].get_basis().qloc(),l);
    }
    
    param1d U = P.fill_array1d<double>("U", "Uorb", F[0].orbitals(), 0);
    if (isfinite(U.a.sum()))
    {
        this->set_name("Hubbard");
    }
    else
    {
        this->set_name("U=∞-Hubbard");
    }
    
    PushType<SiteOperator<Symmetry,double>,double> pushlist;
    std::vector<std::vector<std::string>> labellist;
    HubbardSU2xU1::set_operators(F, P, pushlist, labellist, boundary);
    add_operators(F, P, pushlist, labellist, boundary);
    
    this->construct_from_pushlist(pushlist, labellist, Lcell);
    this->finalize(PROP::COMPRESS, P.get<size_t>("maxPower"));
    
    this->precalc_TwoSiteData();
}
 
void HubbardSU2::
add_operators (const std::vector<FermionBase<Symmetry> > &F, const ParamHandler &P, PushType<SiteOperator<Symmetry,double>,double>& pushlist, std::vector<std::vector<std::string>>& labellist, const BC boundary)
{
    std::size_t Lcell = P.size();
    std::size_t N_sites = F.size();
    
    for(std::size_t loc=0; loc<N_sites; ++loc)
    {
        std::size_t orbitals = F[loc].orbitals();
        // Can also implement superconducting terms here
    }
}
 
} // end namespace VMPS::models
 
#endif