1,622 research outputs found
Quantum Phases of the Shastry-Sutherland Kondo Lattice: Implications for the Global Phase Diagram of Heavy Fermion Metals
Considerable recent theoretical and experimental efforts have been devoted to
the study of quantum criticality and novel phases of antiferromagnetic
heavy-fermion metals. In particular, quantum phase transitions have been
discovered in the compound YbPtPb. These developments have motivated us
to study the competition between the RKKY and Kondo interactions on the
Shastry-Sutherland lattice. We determine the zero-temperature phase diagram as
a function of magnetic frustration and Kondo coupling within a slave-fermion
approach. Pertinent phases include the Shastry-Sutherland valence bond solid
and heavy Fermi liquid. In the presence of antiferromagnetic order, our
zero-temperature phase diagram is remarkably similar to the global phase
diagram proposed earlier based on general grounds. We discuss the implications
of our results for the experiments on YbPtPb and other geometrically
frustrated heavy fermion compounds.Comment: 5 pages 4 figures - Supplementary Material 4 pages 6 figures. Updated
with published versio
Cluster Extended Dynamical Mean Field Approach and Unconventional Superconductivity
The extended dynamical mean field theory has played an important role in the
study of quantum phase transitions in heavy fermion systems. In order to
incorporate the physics of unconventional superconductivity, we develop a
cluster version of the extended dynamical mean field theory. In this approach,
we show how magnetic order and superconductivity develop as a result of
inter-site spin exchange interactions, and analyze in some detail the form of
correlation functions. We also discuss the methods that can be used to solve
the dynamical equations associated with this approach. Finally, we consider
different settings in which our approach can be applied, including the periodic
Anderson model for heavy fermion systems.Comment: 15 pages, 2 figures, Replaced with published versio
Frustration and Multicriticality in the Antiferromagnetic Spin-1 Chain
We study the spin Heisenberg chain, with nearest neighbor, next nearest
neighbor () and biquadratic () interactions using a combination
of the density matrix renormalization group (DMRG), an analytic variational
matrix product state wavefunction, and non-Abelian bosonization. We study the
effect of frustration () on the Haldane phase with
which reveals a rich phase diagram. For , we establish the
existence of a spontaneously dimerized phase for large ,
separated from the Haldane phase by the critical line of
second-order phase transitions connected to the Takhtajan--Babudjian integrable
point . In the opposite regime, , the
transition from the Haldane phase becomes first-order into the next nearest
neighbor (NNN) AKLT phase. Based on field theoretical arguments and DMRG
calculations, we conjecture that these two regimes are separated by a
multicritical point () of a different universality
class, described by the Wess--Zumino--Witten critical theory. From
the DMRG calculations we estimate this multicritical point to lie in the range
and . We find that the
dimerized and NNN-AKLT phases are separated by a line of first-order phase
transitions that terminates at the multicritical point. Inside the Haldane
phase, we show the existence of two incommensurate crossovers: the Lifshitz
transition and the disorder transition of the first kind, marking
incommensurate correlations in momentum and real space, respectively. We show
these crossover lines stretch across the entire phase diagram,
merging into a single incommensurate-to-commensurate transition line for
negative outside the Haldane phase.Comment: 25 pages, 24 figures, updated with published versio
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