Annotated Publications for James K. Freericks
Review Articles
 J. K. Freericks
and V. Zlatic',
Exact dynamical mean field theory of the FalicovKimball model,
Rev. Mod. Phys. 75, 13331382 (2003).
A comprehensive review of equilibrium properties of the FalicovKimball
model, solved with dynamical mean field theory. The formalism is developed
from a pathintegral approach.
 J. K. Freericks,
B. K. Nikolic,
and P. Miller,
Optimizing the speed of a Josephson junction with dynamical meanfield theory,
Int. J. Mod. Phys. B 16, 531561 (2002).
A review of the application of the local approximation and the
FalicovKimball model to the theory of Josephson junctions with barriers
tuned near the metalinsulator transition.

V. Zlatic',
J. K. Freericks,
R. Lemanski, and
G. Czycholl,
Exact solution of the multicomponent FalicovKimball model in infinite
dimensions, Phil. Mag. B 81, 1443 (2001).
A mini review of the FalicovKimball model that emphasizes an equation
of motion approach. Properties of both conduction and localized electrons
are included as well as a discussion of spontaneous hybridization.

Th. Pruschke,
M. Jarrell,
and J. K. Freericks,
Anomalous NormalState Properties of HighTc Superconductors 
Intrinsic Properties of Strongly Correlated Electron Systems?, Adv. Phys.
44 187210 (1995).
A short review of dynamical mean field theory for the Hubbard model
with an emphasis on transport properties.

J. K. Freericks
and M. Jarrell,
Simulation of the electronphonon
interaction in infinite dimensions, in Computer Simulations in
Condensed Matter Physics VII,
edited by D. P. Landau, K. K. Mon, and H.B.
Schuttler (SpringerVerlag, Heidelberg, Berlin, 1994).
A short review of the numerical techniques for performing quantum
Monte carlo simulations of the electronphonon problem in infinite
dimensions.
Josephson Junctions

B. K. Nikolic,
J. K. Freericks,
and P. Miller,
Reduction of Josephson critical current in short ballistic SNS weak
links, Phys. Rev. B 64, 21250714 (2001).
B. K. Nikolic,
J. K. Freericks,
and P. Miller,
Suppression of the ``quasiclassical'' proximity gap in
correlatedmetalsuperconductor structures,
Phys. Rev. Lett. 88, 07700214 (2002);
Virtual Journal of Nanoscale Science & Technology, Vol. 5,
Iss. 7.
B. K. Nikolic,
J. K. Freericks,
and P. Miller,
Equilibrium properties of doublescreeneddipolebarrier SINIS Josephson
junctions, Phys. Rev. B 65, 064529111 (2002);
Virtual Journal of Applications of Superconductivity, Vol. 2,
Iss. 3.
P. Miller and
J. K. Freericks,
Microscopic selfconsistent theory of
Josephson junctions including dynamical electron correlations,
J. Phys.: Conden. Mat. 13 31873213 (2001)
In this series of papers, we generalize dynamical mean field theory to solve
inhomogeneous systems in the superconducting phase. We discover
a number of new results that arise from the selfconsistent description
of a Josephson junction including (i) the proposal that SNSNS structures with
a narrow S layer within the normal metal barrier can have dramatically
improved characteristic voltages; (ii) the suppresion of the quasiclassical
minigap due to electron correlations; (iii) the reduction of characteristic
voltage due to Schottkylike charge rearrangements at the superconductornormal
metal interface; and (iv) a reduction of the characteristic voltage
due to the proximity and inverse proximity effects in ballistic junctions.

J. K. Freericks,
B. K. Nikolic,
and P. Miller,
SuperconductorCorrelated MetalSuperconductor
Josephson junctions: an optimized class for high speed digital electronics,
(Proceedings of the Applied Superconductivity Conference, Houston, Texas)
IEEE Trans. Appl. Supercond. 13, 1089 (2003).
J. K. Freericks,
B. K. Nikolic,
and P. Miller,
Temperature dependence of SuperconductorCorrelated MetalSuperconductor
Josephson junctions, Appl. Phys. Lett. 82, 970972 (2003);
Virtual Journal of Applications of Superconductivity, 4, Issue 4
(2003);
Erratum
Appl. Phys. Lett. 83, 1275 (2003).
J. K. Freericks,
B. K. Nikolic,
and P. Miller,
Tuning a Josephson junction through a quantum critical point,
Phys. Rev. B 64, 054511 (2001).
In this series of papers, we concentrate on what happens to a Josephson
junction as the barrier material is tuned from a metal to an insulator.
We find a number of interesting resuts, including the possibility of
having selfshunted junctions that have the fastest switching times.
Superconductivity in real materials

J. K. Freericks,
Amy Y. Liu,
A. Quandt,
and J. Geerk,
Nonconstant electronic density of states tunneling inversion for A15
superconductors: Nb_{3}Sn,
Phys. Rev. B 65, 224510110 (2002).
We reexamine the tunneling data for A15 compounds using a tunneling
formalism that incorporates the nonconstant electronic density of states
that is calculated with density functional theory. The sharp peak in
the DOS modifies the tunneling conductance, but it is not enough to
fully explain the socalled "overswing".

Sven P. Rudin,
Amy Y. Liu,
J. K. Freericks,
and A. Quandt,
Comparison of structural transformations and superconductivity in
compressed Sulfur and Selenium,
Phys. Rev. B 63, 224107 (2001).
J. K. Freericks,
S. P. Rudin,
and A. Y. Liu,
Firstprinciples determination of superconducting properties of metals,
Physica B 284288, 425426 (2000)
This work plots out the phase diagram of chalcogenides under high
pressure. Sulfur becomes the highest temperature elemental
superconductor when it metallizes, but has large changes in Tc as the
pressure tunes it through a series of structural transitions. Selenium
and Tellurium behave in a similar fashion, but never are stabilized in
a simplecubic phase as Sulfur is.

A. Y. Liu,,
A. A. Quong,
J. K. Freericks,
E. J. Nicol,
and E. C. Jones,
Structural phase stability and electronphonon coupling in Lithium,
Phys. Rev. B 59, 40284035 (1999).
This paper deals with a longstanding puzzle: why is it that Lithium and
Aluminum have almost the same electronphonon coupling but Aluminun
superconducts at about 1K, while Lithium is not superconducting down to 0.004K?
We show that the stable lowtemperature phase of Lithium (which is determined
by an ``honest'' quasiharmonic analysis) has a smaller
electronphonon coupling and conventional theory could explain a
superconducting Tc down to about 0.001K beyond which other explanations
would need to be found to resolve the puzzle. Experiments at Berkeley
have not found any sign of superconductivity down to 0.005K, but they
did see a large Curielike magnetic response, so Lithium may have some
more surprises for us.

S. P. Rudin, R. Bauer,
A. Y. Liu, and
J. K. Freericks,
Reevaluating electronphonon coupling strengths: Indium as a
test case for ab initio and
manybodytheory methods, Phys. Rev. B 58, 1451114517 (1998).
J. K. Freericks,
E. J. Nicol,
A. Y. Liu,
and A. A. Quong, Vertexcorrected tunneling inversion in superconductors,
Czechoslovak Journal of Physics 46, Supplement S2,
603604 (1996).
Here we examine how to calculate the tunneling density of states
of Indium using only one adjustable parameterthe Coulomb pseudopotential.
We find that our theoretical results are as accurate as an experimental
fit to the data (better than one part in 10,000), which illustrates that
current theoretical methods can rival those of experiment for lowtemperature
superconductors. In the process, we discovered that even though the data
can be fit quite accurately, the value of the electronphonon coupling may
have errors as high as 20%.

J. K. Freericks,
E. J. Nicol,
A. Y. Liu,
and A. A. Quong,
Vertexcorrected tunneling inversion in electronphonon
mediated superconductors: Pb, Phys. Rev. B, 55,
1165111658 (1997).
We generalize the conventional MigdalEliashberg theory to include
vertex corrections and see if effects of vertex corrections can be seen
in Lead. We find that the effects of the vertex corrections are just on the
edge of being able to be seen in Lead (the difficulty arises from the
very low phonon frequencies in Lead, which suppress vertex correction
effects). This technique can be employed on other materials like
the fullerenes or cubic perovskites, whenever high quality tunneling data
is produced for them.
Raman scattering, optical conductivity, and transport

J. K. Freericks,
T. P. Devereaux, and
R. Bulla,
Inelastic light scattering and the correlated metalinsulator transition,
(Proceedings of the NATO ARW on strongly correlated electrons, Hvar, Croatia)
Nato Science series II: Mathematics Physics and Chemistry: Vol. 110 (Kluwer,
Dordrecht, 2003), p. 115122.
J. K. Freericks,
T. P. Devereaux, and
R. Bulla,
Inelastic Light Scattering
and the Correlated metalInsulator Transition, (Proceedings of the
Strongly Correlated Electrons conference, Krakow, Poland)
Acta Physica Polonica B 34, 737748 (2003).
J. K. Freericks,
T. P. Devereaux,
R. Bulla,
and
Th. Pruschke,
Nonresonant inelastic light scattering in the Hubbard model,
Phys. Rev. B 67, 15510218 (2003).
F. Venturini, M. Opel,
T. P. Devereaux,
J. K. Freericks, I. Tutto, B. Revaz,
E. Walker, H. Berger, L. Forro, and R. Hackl,
Observation of an unconventional
metalinsulator transition in overdoped CuO_{2} compounds,
Phys. Rev. Lett. 89, 10700314 (2002).
J. K. Freericks,
T. P. Devereaux, and
R. Bulla,
An exact theory for Raman scattering in correlated metals and
insulators, Phys. Rev. B 64, 233114 (2001).
J. K. Freericks
and T. P. Devereaux,
Raman scattering through a metalinsulator transition,
Phys. Rev. B 64, 125110 (2001).
J. K. Freericks,
T. P. Devereaux, and
R. Bulla,
B1g Raman scattering through a quantum critical point,
(Proceedings of the XIIth school of modern physics on
phase transitions and critical phenomena, Ladek Zrdoj, Poland)
Acta Physica Polonica B 32, 32193232 (2001).
J. K. Freericks
and T. P. Devereaux,
Nonresonant
Raman scattering through a metalinsulator transition: an exact analysis
of the FalicovKimball model, (Proceedings of the Workshop on Soft Matter
Theory, Lviv, Ukraine) Conden. Matter Phys. (Ukraine) 4, 149160
(2001).
This is the first work to calculate a Raman response for a system that
undergoes a metalinsulator transition. We find that our results
are universal on the insulating side of the metalinsulator transition
and display the three fundamental features seen in experiment on
strongly correlated materials: (i) a rapid loss of lowenergy spectral
weight and a gain of highenergy spectral weight as temperature is
lowered; (ii) the appearance of an isosbestic point, where the Raman
response is independent of temperature at a characteristic frequency;
and (iii) the ratio of the range in frequency over which the Raman
response is depleted at low temperature to the onset temperature where
the depletion begins is large. This behavior has been seen SmB_{6},
FeSi, and the hightemperature superconductors. The extension of the
nonresonant work to the resonant case represents one of the most
complex solutions to a manybody problem with DMFT.

J. K. Freericks,
T. P. Devereaux,
R. Bulla,
and
Th. Pruschke,
Nonresonant inelastic light scattering in the Hubbard model,
Phys. Rev. B 68, 075105111 (2003).
T. P. Devereaux,
G. E. D. McCormack and
J. K. Freericks,
Inelastic xray scattering in correlated (Mott) insulators,
Phys. Rev. Lett. 90, 06740214 (2003).
In this work, we focus on the light scattering by Xrays which can exchange
both momentum and energy with the electronic charge excitations of
the correlated material. We see dispersion of some quantities, the
appearance of isosbestic points throughout the Brillouin zone, and a way
to test for the effects of nonlocal charge fluctuations by appropriately
using polarizers. Further extensions will include a description of the
resonant inelastic xray scattering process which is an interesting new
experimental technique employed to examine charge excitations of
correlated materials.

J. K. Freericks,
Crossover from tunneling to incoherent (bulk) transport in a correlated
nanostructure, Appl. Phys. Lett. 84, 13831385 (2004);
Virtual Journal of Nanoscale Science and Technology, 9, Issue 8
(2004);
Virtual Journal of Applications of Superconductivity, 6, Issue 5
(2004).
In this work we examine how the transport in a multilayer nanostructure
changes from tunneling (for thin barriers at low temperature) to incoherent
Ohmic transport (for thick barriers at high temperature). We develop the
theory of a generalized Thouless energy that describes the crossover.
 B. K. Nikolic
and J. K. Freericks,
Mesoscopics in spintronics: Quantum interference effects in spinpolarized
electrons, submitted to Phys. Rev. B.
B. K. Nikolic
and J. K. Freericks,
Mesoscopic spintronics: Fluctuation and localization effects in spinpolarized
quantum transport, Toward the controllable quantum states,
edited by H. Takayanagi and J. Nitta (World Scientific, 2003).
Papers on spintronics and the Rashba coupling.

A. V. Joura, D. O. Demchencko, and
J. K. Freericks,
Thermal transport in the FalicovKimball model on a Bethe lattice,
Phys. Rev. B 69, 16510515 (2004).
J. K. Freericks,
D. Demchenko, A. Joura,
and V. Zlatic',
Optimizing thermal transport in the FalicovKimball model: binaryalloy
picture, Phys. Rev. B 68, 195120112 (2003).
J. K. Freericks
and V. Zlatic',
Thermal transport in the FalicovKimball model,
Phys. Rev. B 64, 245118110 (2001);
Erratum: Phys.
Rev. B 66, 24990112 (2002).
Here we examine what happens to thermal transport properties in the
FalicovKimball model. We are able to explicitly prove the JonsonMahan
theorem and find regions where the thermoelectric figure of merit is
larger than one both at low temperature and high temperature. But it
is likely the low temperature peaks will disappear when phonon thermal
conductivity is included. We also find quite different behavior on the
hypercubic lattice versus the Bethe lattice which is due to anomalous
features associated with the pseudogap nature of the insulating phase
on the hypercubic lattice.

B.M. Letfulov and
J. K. Freericks,
Dynamical meanfield theory of a doubleexchange model with diagonal
disorder, Phys. Rev. B 64, 174409 (2001).
My only paper on the colossal magnetoresistance materials.

M. Jarrell,
J. K. Freericks,
and Th. Pruschke,
Optical conductivity
of the infinitedimensional Hubbard model, Phys. Rev. B 51
, 1170411711 (1995).
Here we examine the appearance of midinfrared response in the optical
conductivity for a correlated metal described by the Hubbard model.
One of the interesting results we find is the appearance of an isosbestic
pointwhere the optical conductivity is independent of electron concentration
at a characteristic frequency.

J. K. Freericks
and L. M. Falicov, Dephasing effects in a
twodimensional magneticbreakdown linkedorbit network: Magnesium, Phys.
Rev. B 39, 56785683 (1989).
My first paper in condensed matter physics, this work examined how
disorder, induced by thermal quenching of ultrapure samples of Magnesium,
modifies the transport of electrons in the presence of a perpendicular
magnetic field. This simple model produced remarkable agreement with
the experimental data that was measured in the sixties.
Models of Strong Electron Correlations
FalicovKimball Model

D. O. Demchencko, A. V. Joura, and
J. K. Freericks,
Effect of particlehole asymmetry on the MottHubbard metalinsulator transition
Phys. Rev. Lett. 92, 21640114 (2004).
This work shows that the metalinsulator transition in dynamical mean
field theory is not always governed by the creation of a pole in
the self energy at the transition.l On systems with a finite bandwidth,
the MIT usually occurs before a pole forms, and the model does not have
any significant change in its properties when a pole subsequenctly forms
at a larger interaction strength.

A. M. Shvaika and
J. K. Freericks,
Equivalence of the FalicovKimball and BrandtMielsch forms for the free energy
of the infinitedimensional FalicovKimball model,
Phys. Rev. B 67, 15310313 (2003).
 This work is almost a textbook derivation of the equivalence of two
apparently different ways to calculate the free energy of the FalicovKimball
model.

R. Lemanski,
J.K. Freericks and G. Banach,
Stripe phases in the
twodimensional FalicovKimball model,
Phys. Rev. Lett. 89 19640314 (2002).
Here we show how stripelike phases naturally arise in the twodimensional
FalicovKimball model as the system changes from a checkerboard pattern
at half filling to a segregated system at low filling.

J. K. Freericks,
E. H. Lieb,
and D. Ueltschi,
Phase separation due to quantum mechanical
correlations, Phys. Rev. Lett. 88, 10640114 (2002).
J. K. Freericks,
E. H. Lieb,
and D. Ueltschi,
Segregation in the
FalicovKimball model, Commun. Math. Phys. 227, 243279 (2002).
In this work, we solved a longstanding problem that proved that the
FalicovKimball model always phase separates when the interaction strength is
large enough on any lattice in any dimension.

Ling Chen, B. A. Jones, and
J. K. Freericks,
Chargedensitywave order parameter of the FalicovKimball model
in infinite dimensions, Phys. Rev. B 68, 15310214 (2003).
Ch. Gruber, N. Macris, Ph. Royer, and
J. K. Freericks,
Higher period ordered phases on the Bethe lattice,
Phys. Rev. B. 63, 165111111 (2001).
We examine the chargedensity wave ordered phase of the FalicovKimball
model. In the 2003 paper, we examine the order parameter as a function of
temperature, and see that it has an anomalous shape for weak coupling.
In the 2001 paper, we explicitly show how to generate a periodthree phase on an
infinitecoordination Bethe lattice. Surprisingly, these phases are
stable only at very low temperature, and typically have firstorder
phase transitions.
 J. K. Freericks
and P. Miller,
Dynamical charge susceptibility of the spinless FalicovKimball model,
Phys. Rev. B 62, 1002210032 (2000).
We use KadanoffBaym theory to derive the frequency dependent
charge susceptibility for the FalicovKimball model, which is one
of the few manybody systems that one can exactly solve for a dynamical
susceptibility. These results were used heavily in deriving Raman
scattering behavior for nontrivial symmetry sectors.

B.M. Letfulov and
J. K. Freericks,
Phase separation in the combined
FalicovKimball and static Holstein model, Phys. Rev. B 66,
03310214 (2002).
J. K. Freericks
and R. Lemanski,
Segregation and chargedensitywave order in the spinless
FalicovKimball model, Phys. Rev. B 61 1343813444 (2000).
J. K. Freericks,
Ch. Gruber, and N. Macris,
Phase separation and the segregation principle in
the infiniteU spinless FalicovKimball model,
Phys. Rev. B 60 16171626 (1999).
J. K. Freericks,
Ch. Gruber, and N. Macris,
Phase separation in the binaryalloy
problem: the onedimensional spinless FalicovKimball model,
Phys. Rev. B 53, 1618916196 (1996).
J. K. Freericks,
Local approximation to the spinless FalicovKimball
model, Phys. Rev. B 48, 1479714801 (1993).
J. K. Freericks,
Spinless FalicovKimball model (annealed
binary alloy) from large to small dimensions, Phys. Rev. B 47,
92639272 (1993).
J. K. Freericks
and L. M. Falicov,
Twostate onedimensional
spinless Fermi gas, Phys. Rev. B 41, 21632172 (1990).
These series of papers examine phase separation and chargedensitywave
order in the FalicovKimball model. Results range from numerical
calculations on onedimensional or infinitedimensional systems,
to rigorous results for small or large coupling strength. One of the
interesting results coming from this work is the strong tendency for
electron repulsion to favor phase separation, which has been seen in the
chargestripe phase of the cuprate materials.
 Woonki Chung
and J. K. Freericks,
Competition between phase separation and ``classical'' intermediate
valence in an exactly solved model, Phys. Rev. Lett. 84, 24612464
(2000).
Woonki Chung
and J. K. Freericks,
Chargetransfer metalinsulator transitions in the spinonehalf FalicovKimball
model, Phys. Rev. B 57 1195511961 (1998).
J. K. Freericks
and L. M. Falicov,
Thermodynamic model of the
insulatormetal transition in nickel iodide, Phys. Rev. B 45,
18961899 (1992).
These publications examine metalinsulator transitions and
intermediatevalence behavior, providing an exact solution that
proves firstorder transitions exist in the FalicovKimball model.
In addition, we found that phase separation or a direct metalinsulator
transition usually preclude intermediatevalence behavior over a
wide range of parameter space.

V. Zlatic' and
J. K. Freericks,
Describing the valencechange transition
by the DMFT solution of the FalicovKimball model,
(Proceedings of the NATO ARW on strongly correlated electrons, Hvar, Croatia)
to be published (Kluwer).
V. Zlatic' and
J. K. Freericks,
DMFT solution of the FalicovKimball model with an internal structure,
(Proceedings of the Strongly Correlated Electrons conference, Krakow, Poland)
Acta Physica Polonica B 34, 931944 (2003).
J. K. Freericks
and V. Zlatic',
Application of the multicomponent
FalicovKimball model to intermediatevalence materials: YbInCu_{4} and
EuNi_{2}(Si_{1x}Ge_{x})_{2},
(Proceedings of the Physics of Magnetism, Poznan, Poland),
physica status solidi (b) 236, 265271 (2003).
V. Zlatic' and
J. K. Freericks,
Theory of valence transitions in Ytterbium and Europium intermetallics,
(Proceedings of the XIIth school of modern physics on
phase transitions and critical phenomena, Ladek Zrdoj, Poland)
Acta Physica Polonica B 32, 32533266 (2001).
V. Zlatic' and
J. K. Freericks,
Theory of valence transitions in ytterbiumbased compounds,
in Open Problems in Strongly Correlated
Electron Systems, edited by J. Bonca, P. Prelovsek, A. Ramsak,
and S. Sarkar, (Kluwer, Dordrecht, 2001) p. 371380 [NATO Science Series, II.
Mathematics, Physics, and ChemistryVol. 15] (Proceedings of NATO ARW
conference, Bled, Slovenia, 2001).
J. K. Freericks
and V. Zlatic',
Anomalous magnetic response of the spinonehalf
FalicovKimball model, Phys. Rev. B 58 322329 (1998).
Here we examine the anomalous properties of the YbInCu4 system.
We find that this material, which undergoes a finite temperature intermediate
valence phase transition, is described well by the FalicovKimball
model at high temperatures, where a metalinsulator transition drives
the electronic density of states down, so hybridization effects are
not very important. As the temperature is lowered, the system
is described better by a periodic Anderson model. Our initial
interpretation of the data, in terms of illplaced and properly placed
Yb atoms, turned out not to be borne out by experiment.
Hubbard Model
Periodic Anderson Model
 A. N. TahvildarZadeh,
M. Jarrell, Th. Pruschke,
and J. K. Freericks,
Evidence for exhaustion in the conductivity of the
infinitedimensional periodic Anderson model, Phys. Rev. B 60,
1078210787 (1999).
A. N. TahvildarZadeh,
M. Jarrell,
and J. K. Freericks,
Lowtemperature coherence in the periodic Anderson model:
Predictions for photoemission of heavy Fermions, Phys. Rev. Lett.
80 51685171 (1998).
A. N. TahvildarZadeh,
M. Jarrell,
and J. K. Freericks,
Protracted screening in the periodic Anderson model, Phys. Rev. B
55, 33323335 (1997) (Rapid Communication)
This series of papers covers phenomena related to exhaustion physics
in the periodic Anderson model. This occurs when there are fewer
conduction electrons than felectrons to be able to screen all of the
local moments except as a collective process. As a result, there are
interesting predictions about what should be seen in photoemission and
optical conductivity measurements, which agree with that observed for
some heavyfermion or intermediatevalence materials.
Holstein Model

J. K. Freericks
and V. Zlatic',
Gap ratio in anharmonic chargedensitywave systems,
Phys. Rev. B 64, 073109 (2001).
J. K. Freericks,
V. Zlatic',
and M. Jarrell,
Approximate scaling relation for the anharmonic electronphonon problem,
Phys. Rev. B 61, R838841 (2000) (Rapid Communication).
J. K. Freericks,
M. Jarrell,
and G. D. Mahan,
The anharmonic electronphonon problem,
Phys. Rev. Lett. 77, 45884591 (1996);
Erratum: Phys. Rev. Lett. 79, 1783 (1997).
J. K. Freericks
and G. D. Mahan,
Strongcoupling expansions for the anharmonic Holstein
model and for the HolsteinHubbard model, Phys. Rev. B 54,
93729384 (1996);
Erratum: Phys. Rev. B 56, 1132111325 (1997).
Here we examine differences that arise when anharmonic phonons interact
with electrons (as one would normally expect to occur in a real material
where the phonons are not harmonic since the lattice expands when
heated). Surprisingly, we find scaling behavior of our results, which
say that once one maps the anharmonic system onto an equivalent harmonic
system, then both the singleparticle and the twoparticle
properties are essentially the same for harmonic and anharmonic systems.
This is surprising, because it requires scaling behavior for the
transition temperature and the chargedensitywave gap at zero
temperature, which one wouldn't naively expect to scale exactly the
same way with anharmonicity.
 P. Miller,
J. K. Freericks,
and
E. J. Nicol,
Possible experimentally observable effects of vertex corrections in
superconductors, Phys. Rev. B 58, 1449814510 (1998).
J. K. Freericks,
V. Zlatic', Woonki Chung,
and M. Jarrell,
Vertexcorrected perturbation theory for the electronphonon problem
with nonconstant density of states, Phys. Rev. B 58, 1161311623
(1998).
J. K. Freericks
and M. Jarrell,
Iterated perturbation theory for
the attractive Holstein and Hubbard models, Phys. Rev. B 50
, 69396953 (1994).
J. K. Freericks,
Conserving approximations for the attractive
Holstein and Hubbard models, Phys. Rev. B 50, 403417
(1994).
J. K. Freericks
and
D. J. Scalap
ino,
Weakcoupling expansions for
the attractive Holstein and Hubbard models, Phys. Rev. B 49,
63686371 (1994).
E. J. Nicol and
J. K. Freericks,
Vertex corrections to the theory
of superconductivity, Physica C 235240, 23792380
(1994).
J. K. Freericks,
Strongcoupling expansions for the attractive
Holstein and Hubbard models, Phys. Rev. B 48, 38813891
(1993).
This is a series of weak and strongcoupling perturbation series expansions
for the electronphonon problem. We find that in the strongcoupling
limit, the simple perturbative expansions are quite accurate when one is
in the bipolaronic (preformed pair) regime. On the weakcoupling
side, however, we find that virtually nothing allows you to accurately
extend the conventional perturbation theory beyond a coupling strength
on the order of one. We do predict, that the best way to look for
effects of vertex corrections in a real material is through the
isotope effect, which will have very different behavior if vertex
corrections are important.
 J. K. Freericks
and M. Jarrell,
Competition between electronphonon attraction and weak Coulomb
repulsion, Phys. Rev. Lett., 75, 25702573 (1995).
J. K. Freericks,
M. Jarrell, and
D. J. Scalapino,
The electronphonon problem in infinite dimensions, Europhys. Lett.
25, 3742 (1994).
J. K. Freericks
and M. Jarrell,
Simulation of the electronphonon
interaction in infinite dimensions, in Computer Simulations in
Condensed Matter Physics VII,
edited by D. P. Landau, K. K. Mon, and H.B.
Schuttler (SpringerVerlag, Heidelberg, Berlin, 1994).
J. K. Freericks,
M. Jarrell, and
D. J. Scalapino,
Holstein model
in infinite dimensions,
Phys. Rev. B 48, 63026314 (1993).
This is a series of quantum Monte Carlo simulations investigating
properties of harmonic electronphonon systems and examining
the regions of stability for chargedensitywave ordered phases versus
superconductivity. A number of interesting results came out of this
work ranging from unexpected robustness of the chargedensitywave order
at half filling to a Coulomb repulsion, a change in character of the
ground state from one that orders and pairs at Tc to one that has
a preformed pair that condenses at a lower temperature, and
a large reduction in transition temperatures due to vertex corrections.
 J. K. Freericks
and E. H. Lieb,
The ground state of a general
electronphonon Hamiltonian is a spin singlet, Phys. Rev. B 51
, 28122821 (1995).
In this work, we show that the ground state of an electronphonon
system, with a wide range of different (nonlinear) couplings always
contains a spinsinglet state. For a class of models (including the
Holstein model), we show that the ground state is unique, and hence must be
a spin singlet. One consequence of the uniqueness is that there is
no selftrapping transition of a polaron, rather it is a smooth
(albeit very rapid) transition from a delocalized to a localized
``quasiparticle.''
Bose Hubbard Model
 M. Niemeyer,
J. K. Freericks,
and H. Monien,
Strongcoupling perturbation theory for the twodimensional BoseHubbard
model in a magnetic field,
Phys. Rev. B 60 23572362 (1999).
J. K. Freericks
and H. Monien,
Strongcoupling expansions for the pure and disordered Bose
Hubbard model, Phys. Rev. B 53, 26912700 (1996).
J. K. Freericks
and H. Monien,
Phase diagram of the Bose Hubbard
model, Europhys. Lett. 26, 545550 (1994).
H. Monien and
J. K. Freericks,
Phase diagram of the Bose Hubbard
model, in Strongly Correlated Electronic Materials Los Alamos Symposium
1993, edited by K. Bedell, E. Abrahams, A. Balatsky, D. Meltzer, and
Z. Wang (AddisonWesley, New York, 1994).
This work focuses on using strongcoupling perturbation theory to
determine the phase boundary of the bose Hubbard model, which can be
viewed as a model for disordered superconductivity, where there is
local pairing, but no global phase coherence. What is surprising in this
work is that loworder perturbation theory can rival the accuracy of
complicated quantum Monte Carlo simulations, and that one can determine
phase boundaries in the disordered case much more accurately, because one
can explicitly take into account socalled rare regions. Most of the results
of this work was verified either numerically, by performing expansions to
high order, or experimentally (by Mooij's group) on microfabricated
Josephson junction array experiments.
Small Cluster Calculations
 J. K. Freericks
and L. M. Falicov,
Heavyfermion systems in magnetic
fields: the metamagnetic transition, Phys. Rev. B 46,
874879 (1992).
L. M. Falicov and
J. K. Freericks,
Electronic Structure of Highly
Correlated Systems, in Condensed Matter Theories, Vol. 8, edited by
L. Blum and F. Bary Malik (Plenum Press, 1992).
J. K. Freericks,
L. M. Falicov, and D. S. Rokhsar,
Exact solutions
of frustrated ordinary and chiral eightsite Hubbard models, Phys. Rev. B
44, 14581475 (1991).
J. K. Freericks
and L. M. Falicov,
Exact manybody solution of the
periodiccluster tt'J model for cubic systems: groundstate
properties, Phys. Rev. B 42, 49604978 (1990).
This is work performed during my graduateschool days. We examined the
exact solution of a number of Hubbardlike models on small clusters.
Much interesting physics was discovered, especially about the
stability of magnetic phases, and metamagnetism, but I found the
finitesize effects were often too big to be able to make much
progress with this approach.
 J. K. Freericks
and L. M. Falicov, Enlarged symmetry groups of
finitesize clusters with periodic boundary conditions, Lett. Math. Phys.
22, 277285 (1991).
J. K. Freericks
and L. M. Falicov,
Hidden symmetries of finitesize
clusters with periodic boundary conditions, Phys. Rev. B 44,
28952904 (1991).
These results, that finitesize clusters have extra symmetries, is
something that I found to be fascinating when I discovered it to occur
in a general case. Unfortunately, since the extra symmetry leads to
``accidental'' degeneracies in the manybody spectrum, this result
also showed that until the cluster is large enough, finitesize effects
can be very strong, and very difficult to disentangle, by any simple
analysis of the calculated results.
Jim Freericks, Professor of Physics