95 research outputs found
Suppression of superconductivity by Neel-type magnetic fluctuations in the iron pnictides
Motivated by recent experimental detection of Neel-type ()
magnetic fluctuations in some iron pnictides, we study the impact of competing
and spin fluctuations on the superconductivity of these
materials. We show that, counter-intuitively, even short-range, weak Neel
fluctuations strongly suppress the state, with the main effect arising
from a repulsive contribution to the pairing interaction, complemented
by low frequency inelastic scattering. Further increasing the strength of the
Neel fluctuations leads to a low- d-wave state, with a possible
intermediate phase. The results suggest that the absence of
superconductivity in a series of hole-doped pnictides is due to the combination
of short-range Neel fluctuations and pair-breaking impurity scattering, and
also that of optimally doped pnictides could be further increased if
residual fluctuations were reduced.Comment: revised version accepted for publication in PR
Antiphase Stripe Order as the Origin of Electron Pockets Observed in 1/8-Hole-Doped Cuprates
Recent quantum oscillation measurements on underdoped cuprates are shown to
be consistent with the predictions of a mean field theory of the 1/8 magnetic
antiphase stripe order proposed to occur in high- cuprates. In particular,
for intermediate values of the stripe order parameter, the magneto-transport is
found to be dominated by an electron pocket
The antiferromagnetic phase of the Floquet-driven Hubbard model
A saddle point plus fluctuations analysis of the periodically driven
half-filled two-dimensional Hubbard model is performed. For drive frequencies
below the equilibrium gap, we find discontinuous transitions to time-dependent
solutions. A highly excited, generically non-thermal distribution of magnons
occurs even for drive frequencies far above the gap. Above a critical drive
amplitude, the low-energy magnon distribution diverges as the frequency tends
to zero and antiferromagnetism is destroyed, revealing the generic importance
of collective mode excitations arising from a non-equilibrium drive
Efficient DMFT-simulation of the Holstein-Hubbard Model
We present a method for solving impurity models with electron-phonon
coupling, which treats the phonons efficiently and without approximations. The
algorithm is applied to the Holstein-Hubbard model in the dynamical mean field
approximation, where it allows access to strong interactions, very low
temperatures and arbitrary fillings. We show that a renormalized
Migdal-Eliashberg theory provides a reasonlable description of the phonon
contribution to the electronic self energy in strongly doped systems, but fails
if the quasiparticle energy becomes of order of the phonon frequency.Comment: Published versio
Emergent properties hidden in plane view: Strong electronic correlations at oxide interfaces
Finding new collective electronic states in materials is one of the
fundamental goals of condensed matter physics. Atomic-scale superlattices
formed from transition metal oxides are a particularly appealing hunting ground
for new physics. In bulk form, transition metal oxides exhibit a remarkable
range of magnetic, superconducting, and multiferroic phases that are of great
scientific interest and are potentially capable of providing innovative energy,
security, electronics and medical technology platforms. In superlattices new
states may emerge at the interfaces where dissimilar materials meet.
Here we illustrate the essential features that make transition metal
oxide-based heterostructures an appealing discovery platform for emergent
properties with a few selected examples, showing how charge redistributes,
magnetism and orbital polarization arises and ferroelectric order emerges from
heterostructures comprised of oxide components with nominally contradictory
behavior with the aim providing insight into the creation and control of novel
behavior at oxide interfaces by suitable mechanical, electrical or optical
boundary conditions and excitations.Comment: 16 pages, 5 figure
A continuous-time solver for quantum impurity models
We present a new continuous time solver for quantum impurity models such as
those relevant to dynamical mean field theory. It is based on a stochastic
sampling of a perturbation expansion in the impurity-bath hybridization
parameter. Comparisons to quantum Monte Carlo and exact diagonalization
calculations confirm the accuracy of the new approach, which allows very
efficient simulations even at low temperatures and for strong interactions. As
examples of the power of the method we present results for the temperature
dependence of the kinetic energy and the free energy, enabling an accurate
location of the temperature-driven metal-insulator transition.Comment: Published versio
Trigonal Symmetry Breaking and its Electronic Effects in Two-Dimensional Dihalides and Trihalides
We study the consequences of the approximately trigonal () point
symmetry of the transition metal (M) site in two-dimensional van der Waals
MX dihalides and MX trihalides. The trigonal symmetry leads to a 2-2-1
orbital splitting of the transition metal shell, which may be tuned by the
interlayer distance, and changes in the ligand-ligand bond lengths. Orbital
order coupled to various lower symmetry lattice modes may lift the remaining
orbital degeneracies, and we explain how these may support unique electronic
states using ZrI and CuCl as examples, and offer a brief overview of
possible electronic configurations in this class of materials. By building and
analysing Wannier models adapted to the appropriate symmetry we examine how the
interplay among trigonal symmetry, electronic correlation effects, and -
orbital charge transfer leads to insulating, orbitally polarized magnetic
and/or orbital-selective Mott states. Our work establishes a rigorous framework
to understand, control, and tune the electronic states in low-dimensional
correlated halides. Our analysis shows that trigonal symmetry and its breaking
is a key feature of the 2D halides that needs to be accounted for in search of
novel electronic states in materials ranging from CrI to -RuCl
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