lda+dmft and beyond - iidmft-2.pdf · condition for Δand relation with dmft to determine Δ, we...
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LDA+DMFT and beyond - IIA. Lichtenstein
University of Hamburg
In collaborations with:A. Poteryaev(Ekaterinburg), M. Rozenberg, S. Biermann, A. Georges (Paris)L. Chioncel (Graz), I. di Marco, M. Katsnelson (Nijmegen)E. Pavarini (Jülich), O.K. Andersen (Stuttgart)G. Kotliar (Rutgers), S. Savrasov (Devis), A. Rubtsov (Moscow)F. Lechermann, H. Hafermann, T. Wehling, C. Jung, M. Karolak (Hamburg)
http://www.physnet.uni-hamburg.de/hp/alichten/lectures/LDA+DMFT-2.pdf
Outline-III
• Non-local Correlation Effects
• Cluster DMFT Scheme
• LDA+cDMFT for Real Systems
• Dual Fermions
• Future of first-principle LDA+DMFT
Magnetic nanostructures
Quantum corralQuantum corralD. D. EiglerEigler (IBM)(IBM)
S. S. OtteOtte et. al.et. al.(IBM)(IBM)Fe
Co
Dynamical Mean-Field Theory
Σ Σ Σ
Σ
Σ
Σ
ΣΣ
U
U
G( ’)τ−τ
ττ’
Review: A. Georges, et. al. RMP, 1996
-
Cluster DMFT schemeFree cluster
Periodic cluster
1G−Σ −-1= G
1
1
[ ( ) ( )]k
G i H k
G
ω μ ω −
−
= + − −Σ
= +Σ
∑-1G
1
1
[ ( ) ( , )]k
ab ai ij jbij
ij ij ia ab bjab
G i H k k
i t G t
G G G G G
ω μ ω
ω μ
−
−
= + − −Σ
= + −
= −
∑
∑
∑
-1G
AFM and d-wave in HTSC
A.L. and M.Katsnelson PRB(2000)
AFM+d-wave in CDMFT
In superconducting state:
Coexistence of AFM and d-wave
0 1
23
Magnetism vs. Kondo resonance
-4 -2 0 2 4
0.0
0.2
0.4
0.6
DO
S
Energy
U=2.4, J=-0.2 and J=0, β=64
Three impurity atoms with Hubbard
repulsion and exchange interaction
M. M. CrommieCrommie, PRL(2001), PRL(2001) CTCT--QMC:QMC: single single vs.vs. trimertrimerV. V. SavkinSavkin et al, PRL (2005)et al, PRL (2005)
#1#1 #2#2
Σ Σ Σ
Σ Σ
Σ Σ
Σ
Σ
Σ
Σ Σ Σ Σ
Cluster DMFT
ΣU
( )ττ ′−0G
ΣU
V
M. Hettler et al, PRB 58, 7475 (1998)A. L. and M. Katsnelson, PRB 62, R9283 (2000)G. Kotliar, et al, PRL 87, 186401 (2001)
Double Bethe lattice: AFM vs. Kondo
Z Z →→ ∞∞
Z=3Z=3
Exact cluster DMFTExact cluster DMFT MIT: G. MMIT: G. Mööllerller, et. al. 1999, et. al. 1999
QMC:QMC:U=2U=2W=2W=2t=0.5t=0.5ββ=10=10 t
m0.5
0.1p
jiU t U
t t
P
J~tJ~tpp
Double-Bethe Lattice: exact C-DMFT
A. RuckensteinPRB (1999)
Self-consistent condition: C-DMFT
AF-between plane AF-plane
Finite temperature phase diagram
• order-disorder transition at t⊥ / t=√2 for large U• MIT for intermediate U
Density of States: large U
Spin-correlations: large U
CT-QMC measuring χ in imaginary time
Dynamical susceptibility
M. Marezio et al., (1972)
TMTM--Oxide VOOxide VO22: singlet formation: singlet formation
Metal
Tem
pera
ture
(K)
Insulator
Rutile structure Monoclinic distortion inthe insulating phase
j
i
G ω( )ij
U
U
tij
U/t
ε εi jb
a
LH
UH
Correlation vs. Bonding
Local Green function
Veg w Ww Veg WW W Va1g
Matrix of intersite Coulomb interaction
IntersiteIntersite interaction: Tiinteraction: Ti22OO33
Corundum structurefor low and high temperature phases
Efa
1g
a1g*
Ve
g
WV
a1g
eg
eg
a1g
a1g
w
V-V pair in V2O3
j
i
G ω( )ij
ae1
The Goodenough diagram
E
O2pO2p
EFa1g
ega1g
Ti2O3 V2O3
eg
eg
Ti2O3 – d1 state1-st order MITAround 470KWidth 250 K
LDA givesMetallic state
Problem:Bonding vs. U
LDA electronic structureLDA electronic structure
gg aat 11 −
gg ea εε −1
TiTid −
0.21 eV
-0.85 eV
2.57 Å
0.23 eV
-0.63 eV
2.72 Å
-2 -1 0 1 2 3Energy, eV
0
1
2
DO
S, s
tate
s/eV
Totale
g
a1g
VOVO22 TiTi22OO33
-2 -1 0 1 2 3Energy, eV
0
1
2
DO
S, s
tate
s/eV
Totale
g
a1g
gg aat 11 −
gg ea εε −1
VVd −
LT HT
0.29 eV
-0.81 eV
2.53 Å
0.15 eV
-0.31 eV
2.75 Å
M1 R
-4 -2 0 2 4 6Energy, eV
0.0
0.5
1.0
1.5
2.0
DO
S, s
tate
s/eV
Totale
g
a1g
-4 -2 0 2 4 6Energy, eV
0.0
0.5
1.0
1.5
2.0
DO
S, s
tate
s/eV
Totale
g
a1g
U = 2, J = 0.5, W = 0.5β = 20 eV-1, LT structure
U = 2, J = 0.5, W = 0.5β = 10 eV-1, HT structure
Cluster LDA+DMFT: TiCluster LDA+DMFT: Ti22OO33
K. Smith et al., PRB 38, 5965 (1988)
10iω
n, eV
-0.2
-0.1
0.0
Σ, e
V
ReΣa
1g-a
1g
ImΣa
1g
ReΣ’a
1g-a
1g
A. Poteryaev, et al, PRL93, 086401 (2004)
Cluster-DMFT results for VO2
0
0.2
0.4
0.6
0.8
1.0
−2 0 2 4
U=4eV J=0.68eV
ρ(ω)
ω[eV]
LDA VO2
rutileDMFT
(dashed)(solid)
0
0.5
1.0
1.5
−4 −2 0 2 4
DOS VO2−M1
LDA
ω [eV]
cluster DMFT
(dashed)
(solid)
U = 4 eV, J=0.68 eV β = 20 eV-1Rutile
M1
New photoemission from Tjeng’s groupT. C. Koethe, et al. PRL (2006)
Sharp peak below the gap is NOT a Hubbard band !
S. Biermann, et al, PRL 94, 026404 (2005)
Beyond DMFT: Dual Fermion scheme
A. Rubtsov, et al, Phys. Rev. B 77, 033101 (2008)
General Lattice Action
Optimal Local Action with hybridization Δω
Lattice-Impurity connection:
Dual FermionsGaussian path-integral
With new Action:
here:
gω and χν,ν‘,ω from DMFT
Dual Fermion Action: Details
Dual and Lattice Green’s Functions
Basic diagrams for dual self-energy
Lines denote the renormalized Green’s function.
A. Rubtsov, et al., Phys. Rev. B 79, 045133 (2009)
Condition for Δ and relation with DMFT
To determine Δ, we require that Hartree correction in dual variables vanishes.If no higher diagrams are taken into account, one obtains DMFT:
Higher-order diagrams give corrections to the DMFT self-energy, and already the leading-order correction is nonlocal.
Σ(k,ω)
Gd=GDMFT-g
Self-consistent DF-scheme
2d Hubbard: Im Σ(k, ω=0)
10 20 30 40 50 60
10
20
30
40
50
60
Im Σ(0,0)=-0.06
Im Σ(0,π)=-8
kx
kyIm Σ(0,0)=-0.04
Im Σ(0,π)=-0.08
kx
kyIm Σ(0,0)=-0.04
U=1 U=2
A. Rubtsov, et al, Phys. Rev. B (2008)
AFM – symmetry breaking
Pseudogap in HTSC: dual fermions
A. Rubtsov et alPRB (2009)
2d: U=4 W=2t/t’=-0.3
FSΣ
Quasiparticle dispersion
Cluster Dual Fermions: 1d-test, n=1
H. Hafermann, et al. JETP Lett (2007), arXiv:0707.4022
Two-particle Green-Functions
Bethe-Salpeter Equations
Susceptibility: DF vs.DMFT
Convergence of Dual Fermions: 2d
=1
H. Hafermann, PRL 102, 206401 (2009)
Susceptibility: 2d – Hubbard model
Future of first-princuple DMFT
• Accurate description of screen interaction (GW)
• Exact double-counting correction (Vxc-Σ)
• Optimal local basis set (Wannier)
• Accurate impurity solver (CT-QMC)
• Non-local correction (CDMFT, GW+DMFT, DF)
Conclusions
Cluster generalization of DMFT is easy to do in the Matrix-DMFT formalism Cluster LDA+DMFT method can be useful for the short-range non-local correlations in solids.Dual Fermion formalism can described k-dependence of self-energy for correlated systems