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BATH.f90
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BATH.f90
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!###############################################################
! PROGRAM : BATH
! TYPE : Module
! PURPOSE : Constructs some functions used in other places.
! AUTHORS : Adriano Amaricci
! LAST UPDATE: 07/2009
!###############################################################
module BATH
USE VARS_GLOBAL
implicit none
private
integer,parameter :: Lw=2048 !# of frequencies
real(8),allocatable,dimension(:) :: bath_dens,wfreq
public :: get_thermostat_bath
contains
!+-------------------------------------------------------------------+
!PURPOSE : Build the Bath part of the system using exclusively time
!dependent formalism. The bath is not interacting so it is
! time translation invariant.
!+-------------------------------------------------------------------+
subroutine get_thermostat_bath()
integer :: iw,i,j
real(8) :: en,w,dw,wfin,wini
complex(8) :: peso
real(8) :: ngtr,nless,arg
call msg("Get Bath. Type: "//bold_green(trim(adjustl(trim(bath_type))))//" dissipative bath",id=0)
call create_data_dir("Bath")
allocate(bath_dens(Lw),wfreq(Lw))
select case(trim(adjustl(trim(bath_type))))
case("bethe")
wfin = 2.d0*Wbath ; wini=-wfin
wfreq = linspace(wini,wfin,Lw,mesh=dw)
call get_bath_bethe_dos()
case("gaussian")
wfin = 4.d0*Wbath ; wini=-wfin
wfreq= linspace(wini,wfin,Lw,mesh=dw)
call get_bath_gaussian_dos()
case ("constant")
wfin = 2.d0*Wbath ; wini=-wfin
wfreq = linspace(wini,wfin,Lw,mesh=dw)
call get_bath_constant_dos()
case default
call abort("Bath type:"//trim(adjustl(trim(bath_type)))//" not supported. Accepted values are: constant,gaussian,bethe.")
end select
S0=zero
do iw=1,Lw
en = wfreq(iw)
nless= fermi0(en,beta)
ngtr = fermi0(en,beta)-1.d0 !it absorbs the minus sign of the greater functions
do i=0,nstep
do j=0,nstep
peso=exp(-xi*(t(i)-t(j))*en)
S0%less(i,j)=S0%less(i,j)+ xi*Vpd**2*nless*peso*bath_dens(iw)*dw
S0%gtr(i,j) =S0%gtr(i,j) + xi*Vpd**2*ngtr*peso*bath_dens(iw)*dw
enddo
enddo
enddo
if(mpiID==0)then
call write_keldysh_contour_gf(S0,"Bath/S0")
call splot("Bath/DOSbath.lattice",wfreq,bath_dens)
if(plot3D)call plot_keldysh_contour_gf(S0,t(0:),"PLOT/S0")
endif
end subroutine get_thermostat_bath
!********************************************************************
!********************************************************************
!********************************************************************
!+-----------------------------------------------------------------+
!PURPOSE : Build constant BATH
!+-----------------------------------------------------------------+
subroutine get_bath_constant_dos()
integer :: i
real(8) :: w
do i=1,Lw
w=wfreq(i)
bath_dens(i)= heaviside(Wbath-abs(w))/(2.d0*Wbath)
enddo
end subroutine get_bath_constant_dos
!********************************************************************
!********************************************************************
!********************************************************************
!+-----------------------------------------------------------------+
!PURPOSE : Build BATH dispersion arrays \epsilon_bath(\ka) = bath_epski(i)
!+-----------------------------------------------------------------+
subroutine get_bath_gaussian_dos()
integer :: i,ik
real(8) :: w,sig,alpha
complex(8) :: gf,zeta
bath_dens = exp(-0.5d0*(wfreq/Wbath)**2)/(sqrt(pi2)*Wbath) !standard Gaussian
!bath_dens = exp(-((wfreq+xmu)/Wbath)**2)/(sqrt(pi)*Wbath) !Camille's choice
! !!w/ erf in frquency space: coded from Abramowitz-Stegun
! do i=-Lw,Lw
! !w=wfreq(i)
! !zeta=cmplx(w+xmu,eps,8)
! !sig=aimag(zeta)/abs(dimag(zeta))
! !gf=-sig*xi*sqrt(pi)*wfun(zeta/Wbath)/Wbath
! !bath_dens(i)=-aimag(gf)/pi
! enddo
end subroutine get_bath_gaussian_dos
!********************************************************************
!********************************************************************
!********************************************************************
!+-----------------------------------------------------------------+
!PURPOSE : Build BATH dispersion arrays \epsilon_bath(\ka) = bath_epski(i)
!+-----------------------------------------------------------------+
subroutine get_bath_bethe_dos()
integer :: i,ik
real(8) :: w,sig,alpha
complex(8) :: gf,zeta
do i=1,Lw
w=wfreq(i)+xmu
zeta=cmplx(w,eps,8)
gf=gfbether(w,zeta,wbath/2.d0)
bath_dens(i)=-aimag(gf)/pi
enddo
end subroutine get_bath_bethe_dos
!********************************************************************
!********************************************************************
!********************************************************************
! !+-------------------------------------------------------------------+
! !PURPOSE : Build the Bath part of the system using frequency domain
! !formalism.
! !COMMENT : Construct the Bath-Sigma functions from freq. domain
! !(that is 'cause you know the analytic expression, same
! !procedure as in IPTkeldysh @equilibrium)
! !This turns out to be the same provided one takes
! !the limit \eta\goto 0.d0
! !+-------------------------------------------------------------------+
! subroutine get_Bath_w
! integer :: i,im
! real(8) :: A,An,w
! complex(8) :: iw,fg
! complex(8),dimension(-nstep:nstep) :: gb0fless,gb0fgtr
! complex(8),dimension(-nstep:nstep) :: gb0tgtr,gb0tless
! print '(A)',"Get Bath:"
! do i=-nstep,nstep
! w = wr(i) ;iw= cmplx(w,eps,8)
! fg=zero
! do im=0,Lmu
! fg=fg + de*bath_dens(im)/(iw-bath_epsik(im))!/dble(Lmu)
! enddo
! A = -aimag(fg)/pi
! An= A*fermi0(w,beta)
! gb0fless(i)= pi2*xi*An
! gb0fgtr(i) = pi2*xi*(An-A)
! enddo
! call fftgf_rw2rt(gb0fless,gb0tless,nstep) ; gb0tless=fmesh/pi2*gb0tless
! call fftgf_rw2rt(gb0fgtr, gb0tgtr,nstep) ; gb0tgtr =fmesh/pi2*gb0tgtr
! gb0tgtr =exa*gb0tgtr
! gb0tless=exa*gb0tless
! !Get the Self-energy contribution of the bath:
! !=================================================
! S0gtr=zero
! S0less=zero
! S0less=Vpd**2*gb0tless
! S0gtr =Vpd**2*gb0tgtr
! call system("mkdir BATH")
! call splot("BATH/bathG0less_t.ipt",t(-nstep:nstep),gb0tless)
! call splot("BATH/bathG0gtr_t.ipt",t(-nstep:nstep),gb0tgtr)
! call splot("BATH/S0less_t.ipt",t(-nstep:nstep),S0less)
! call splot("BATH/S0gtr_t.ipt",t(-nstep:nstep),S0gtr)
! print '(A)',""
! return
! end subroutine Get_Bath_w
!********************************************************************
!********************************************************************
!********************************************************************
end module BATH