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Contents Ann. Phys. 8Ц92011

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Ann. Phys. (Berlin) 523, No. 8 – 9, 583 – 588 (2011) / DOI 10.1002/andp.201152308
CONTENTS
Full text on our homepage at
www.ann-phys.org
Special Topic Issue
Electronic Correlations in Models and Materials
Guest Editors:
Peter van Dongen, Marcus Kollar, and Thomas Pruschke
PREFACE
Page 589 – 590
P. van Dongen, M. Kollar, and T. Pruschke
ORIGINAL ARTICLES
Page 591 – 598
P. Wölfle and E. Abrahams
Quantum critical behavior of heavy fermions: Quasiparticles in
the Gaussian fluctuation regime
Landau quasiparticle (qp) theory may be extended into the non-Fermi liquid
regime of metallic compounds near a quantum critical point (QCP), provided
the width of the quasiparticle states is less than their energy. Sufficiently far
from the QCP, when the critical fluctuations are non-interacting, their influence on the qp properties may be calculated in a controlled way.
Page 599 – 611
H. v. Löhneysen
Electron-electron interactions and the metal-insulator transition
in heavily doped silicon
μ
The metal-insulator (MI) transition in
(c)
N << NO
Si:P can be tuned by varying the P concentration or – for barely insulating
samples – by application of uniaxial
μ
N ~< NO
stress S. On-site Coulomb interactions
lead to the formation of localized magnetic moments and the Kondo effect on the metallic side, and to a Hubbard
splitting of the donor band on the insulating side.
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
584
Page 612 – 620
Contents
P. Sun, M. Søndergaard, B. B. Iversen, and F. Steglich
Strong electron correlations in FeSb2
FeSb2 has been recently identified as a new model system for studying manybody renormalizations in a d-electron based narrow gap semiconducting system, strongly resembling FeSi. The electron-electron correlations in FeSb2
manifest themselves in a wide variety of physical properties including electrical and thermal transport, optical conductivity, magnetic susceptibility, specific heat and so on. The authors review some of the properties that form a set
of experimental evidences revealing a significant role of correlation effects in
FeSb2 .
Page 621 – 628
B. Obert, S. Takei, and W. Metzner
Anomalous criticality near semimetal-to-superfluid quantum
phase transition in a two-dimensional Dirac cone model
The authors analyze the scaling behavior at and near a quantum critical point
separating a semimetallic from a superfluid phase. To this end they compute
the renormalization group flow for a model of attractively interacting electrons with a linear dispersion around a single Dirac point. They study both
ground state and finite temperature properties.
Page 629 – 637
M. Imada, Y. Yamaji, S. Sakai, and Y. Motome
Theory of pseudogap and superconductivity in doped Mott
insulators
Underdoped Mott insulators provide us with a
cofermion
challenge of many-body physics. Recent renewed
understanding is discussed in terms of the evolution of pole and zero structure of the singleparticle Green’s function. Pseudogap as well
quasiparticle
as Fermi arc/pocket structure in the underdoped
cuprates is well reproduced from the recent cluster
extension of the dynamical mean-field theory. Emergent coexisting zeros and
poles set the underdoped Mott insulator apart from the Fermi liquid, separated
by topological transitions. The cofermion proposed as a generalization of exciton in the slave-boson framework accounts for the origin of the zero surface
formation. The cofermion-quasiparticle hybridization gap offers a natural understanding of the pseudogap and various unusual Mottness. Furthermore the
cofermion offers a novel pairing mechanism, where the cofermion has two
roles: It reinforces the Cooper pair as a pair partner of the quasiparticle and
acts as a glue as well. It provides a strong insight for solving the puzzle found
in the dichotomy of the gap structure.
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.ann-phys.org
Ann. Phys. (Berlin) 523, No. 8 – 9 (2011)
Page 638 – 644
585
W. Hanke, Ch. Platt, and R. Thomale
Order-parameter anisotropies in the pnictides: An optimization
principle for multi-band superconductivity
ky/π
Using general arguments of an optimization tak61 59
63
57
ing place between the pair wave function and the
1 49
55
repulsive part of the electron-electron interaction,
51 53
the authors analyze the superconducting gap in
45
43
29 27
47
materials with multiple Fermi-surface (FS) pock31 13
41
25
9
0 17 1
33
ets, with exemplary application to two proto-type
5 23
39
19 21
35
37
ferropnictide setups. The main point is to show
0
1
that the SC state, its gap, and, in particular, its
kx/π
anisotropy in momentum space is determined by
an optimization which determines and optimizes the interplay between the
attractive interaction in the SC-channel and the Coulomb repulsion.
Page 645 – 651
J. Deisenhofer, M. Schmidt, Z. Wang, Ch. Kant, F. Mayr, F. Schrettle,
H.-A. Krug von Nidda, P. Ghigna, V. Tsurkan, and A. Loidl
Lattice vibrations in KCuF3
Page 652 – 663
7.5
(a)
-4
H = 1T
KCuF3
7.0
χ (10 emu/mol)
The authors report on polarization dependent reflectivity measurements
in KCuF3 in the far-infrared frequency regime. The observed IR active phonons at room temperature are in
agreement with the expected modes for
tetragonal symmetry. A splitting of one
mode already at 150 K and the appearance of a new mode in the vicinity of
the Néel temperature is observed.
TN= 40K
6.5
6.0
5.5
5.0
0
100
200
300
T (K)
400
V. Moshnyaga and K. Samwer
Electron-lattice correlations and phase transitions in CMR
manganites
www.ann-phys.org
10000
10
8000
н
Ͳ Ͳ
н
6000
8
6
4000
4
2000
2
0
R3ω (Ω)
CMR (7T), %
Interrelations between global and local
structure and magnetism and transport
in three-dimensional perovskite manganites is reviewed and compared with
recent studies on thin films and superlattices. The concept of correlated JahnTeller polarons is discussed within the
phase separation scenario; their role in
the local and global structural modifications of manganites is demonstrated.
0
0
50
100
150
200
250
300
350
T (K)
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
586
Page 664 – 671
Contents
S. Kirino and K. Ueda
Nonlinear transport through quantum dots studied by the
time-dependent DMRG
Recent developments on studies of transport through quantum dots obtained
by applying the time-dependent density matrix renormalization group method
are summarized. Some new aspects of Kondo physics which appear in
nonequilibrium steady states are discussed both for the single dot case and
for the serially coupled double-quantum-dot case.
Page 672 – 681
A. Georges
Thinking locally: Reflections on Dynamical Mean-Field Theory
from a high-temperature/high-energy perspective
When spatial correlations are short-range, the physics of strongly correlated
systems is controlled by local quantum fluctuations. In those regimes, Dynamical Mean-Field Theory can be viewed as a ‘compass’ which provides
guidance on the relevant degrees of freedom and their effective dynamics over
intermediate energy scales. These intermediate energy scales and associated
crossovers play a crucial role in the physics of strongly correlated materials.
Page 682 – 688
J. Kuneš and V. I. Anisimov
The authors review their investigations of electronic properties of strongly correlated materials
using the combination of first principles electronic
band structures and the dynamical mean-field
theory, so called LDA+DMFT method. Their investigations focus on two phenomena, the spin
state transitions and their relationship to the metalinsulator transition, and the effect of hybridization
between correlated and ligand orbitals in chargetransfer type materials.
Page 689 – 697
Spectral density
Various scenarios of metal-insulator transition in strongly
correlated materials
O-p
eg- π
a1g
eg- σ
v=1.0
v=0.85
v=0.8
-10
-5
0
5
Energy (eV)
H. Lee, Y.-Z. Zhang, H. O. Jeschke, and R. Valentí
Anisotropic two-orbital Hubbard model: Single-site versus
cluster dynamical mean-field theory
The anisotropic two-orbital Hubbard model with different bandwidths and
degrees of frustration in each orbital is investigated in the framework of both
single-site dynamical mean-field theory (DMFT) as well as its cluster extension (DCA) for clusters up to four sites combined with a continuous-time
quantum Monte Carlo algorithm. This model shows a rich phase diagram
which includes the appearance of orbital selective phase transitions, nonFermi liquid behavior as well as antiferromagnetic metallic states.
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.ann-phys.org
Ann. Phys. (Berlin) 523, No. 8 – 9 (2011)
Page 698 – 705
587
A. Toschi, G. Rohringer, A. A. Katanin, and K. Held
Ab initio calculations with the dynamical vertex approximation
The authors propose an approach for
the ab initio calculation of materials
i
j
with strong electronic correlations
W
V
which is based on all local (fully irrei
j
i
j
i
i'
j'
j
+
=
ducible) vertex corrections beyond the
bare Coulomb interaction. It includes the so-called GW and dynamical mean
field theory and important non-local correlations beyond, with a computational effort estimated to be still manageable.
eff
ij
Page 706 – 714
ij
Ch. Jung, A. Wilhelm, H. Hafermann, S. Brener, and A. Lichtenstein
Superperturbation theory on the real-axis
In this article the authors formulate the
superperturbation theory for the Anderson impurity model on the real axis.
The resulting impurity solver allows to
evaluate dynamical quantities without
numerical analytical continuation by
the maximum entropy method or Padé
approximants.
Page 715 – 723
V. Janiš and V. Pokorný
Renormalized perturbation theories of Anderson localization:
Self-consistent two-particle vertices
The effects of quantum coherence on two-particle vertex functions due to impurity scattering of electrons are studied. The authors use the diagrammatic
perturbation expansion in the impurity potential and analyze possible ways
how to introduce renormalizations on the two-particle level.
Page 724 – 731
D. Baeriswyl
Adiabatic continuity and broken symmetry in many-electron
systems: A variational perspective
Variational wave functions are very useful for describing the panoply of
ground states found in interacting many-electron systems. Some particular
trial states are “adiabatically” linked to a reference state, from which they borrow the essential properties. A prominent example is the Gutzwiller ansatz,
where one starts with the filled Fermi sea. To describe symmetry breaking, the
reference state has to be modified accordingly.
www.ann-phys.org
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
588
Contents
Page 732 – 740
D. Müller, S. Pilgram, T. M. Rice, and M. Sigrist
Extending the Gutzwiller approximation for liquid 3 He by
including intersite correlations
Page 741 – 750
0
Gutzwiller approximation
Bond approximation
1/D approximation
Ekin
The simple Gutzwiller approximation,
applied to the approach to Mott localization in a half-filled band Hubbard
model, gives a remarkably good description of the properties of liquid
3
He as the liquid-solid transition is
approached under pressure. Here the
Gutzwiller approximation is extended
to incorporate correlations between
nearest neighbors.
-0.5
-1
0
0.1
0.2
n
0.3
0.4
0.5
R. Trencsényi, K. Gulácsi, E. Kovács, and Z. Gulácsi
Exact ground states for polyphenylene type of hexagon chains
CH 3
A technique based on positive semidefinite operator properties has been used
a)
O
.....
in deducing exact ground states for
CH3
hexagon chains of polyphenylene type
(hexagons interconnected by bonds
b)
.....
build up the 1D periodic structure),
S
placed in a constant external magnetic
field perpendicular to the surface containing the system.
Page 751 – 758
CH3
CH3
O
S
O .....
CH3
CH3
.....
S
R. Shankar
The last word in strong correlations
In the Fractional Quantum Hall Effect (FQHE), in the noninteracting limit,
only a fraction ν of the Lowest Landau Level (LLL) is occupied, producing a
huge degeneracy. Interactions lift this degeneracy and mix in higher LL’s. In
the limit in which we ignore all but the LLL, the kinetic energy is an irrelevant
constant and the ratio of potential to kinetic energy is essentially infinite, making this the most strongly correlated problem imaginable. The Hamiltonian
theory of the FQHE deals with this problem with some success.
Annalen der Physik is indexed in Chemical Abstracts Service/SciFinder, COMPENDEX, Current
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Recognized by the European Physical Society
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.ann-phys.org
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