1,609 research outputs found
Charge transfer excitations, pair density waves, and superconductivity in moiré materials
Transition-metal dichalcogenide (TMD) bilayers are a new class of tunable moiré systems attracting interest as quantum simulators of strongly interacting electrons in two dimensions. In particular, recent theory predicts that the correlated insulator observed in WSe₂/WS₂ at half filling is a charge-transfer insulator similar to cuprates and, upon further hole doping, exhibits a transfer of charge from anionlike to cationlike orbitals at different locations in the moiré unit cell. In this work, we demonstrate that in this doped charge-transfer insulator, tightly bound charge-2e excitations can form to lower the total electrostatic repulsion. This composite excitation, which we dub a trimer, consists of a pair of holes bound to a charge-transfer exciton. When the bandwidth of doped holes is small, trimers crystallize into insulating pair density waves at a sequence of commensurate doping levels. When the bandwidth becomes comparable to the pair binding energy, itinerant holes and charge-2e trimers interact resonantly, leading to unconventional superconductivity similar to superfluidity in an ultracold Fermi gas near Feshbach resonance. Our theory is broadly applicable to strongly interacting charge-transfer insulators, such as WSe₂/WS₂ or TMD homobilayers under an applied electric field
Bridging the Gap: Exploring the Basic Health Insurance Option for New York
Explores New York state's options, costs, and benefits of creating a basic health plan under health reform, including available federal funding, take-up rates by various population groups, types of plans, and impact on state exchange and uninsured rates
Kinetics and thermochemistry of polyatomic free radicals: New results and new understandings
An experimental facility for the study of the chemical kinetics of polyatomic free radicals is described which consists of a heatable tubular reactor coupled to a photoionization mass spectrometer. Its use in different kinds of chemical kinetic studies is also discussed. Examples presented include studies of the C2H3 + O2, C2H3 + HC1, CH3 + O, and CH3 + CH3 reactions. The heat of formation of C2H3 was obtained from the results of the study of the C2H3 + HC1 reaction
A Simple Mechanism for Unconventional Superconductivity in a Repulsive Fermion Model
Motivated by a scarcity of simple and analytically tractable models of
superconductivity from strong repulsive interactions, we introduce a simple
tight-binding lattice model of fermions with repulsive interactions that
exhibits unconventional superconductivity (beyond BCS theory). The model
resembles an idealized conductor-dielectric-conductor trilayer. The Cooper pair
consists of electrons on opposite sides of the dielectric, which mediates the
attraction. In the strong coupling limit, we use degenerate perturbation theory
to show that the model reduces to a superconducting hard-core Bose-Hubbard
model. Above the superconducting critical temperature, an analog of pseudo-gap
physics results where the fermions remain Cooper paired with a large
single-particle energy gap.Comment: 12+12 pages; 3 figures; v5 is a major revision with new additions: a
conductor-dielectric-conductor trilayer interpretation, an elaborated
introduction, figures 1 and 2, and sections 4.3.1 and 5.
Foliated Field Theory and String-Membrane-Net Condensation Picture of Fracton Order
Foliated fracton order is a qualitatively new kind of phase of matter. It is
similar to topological order, but with the fundamental difference that a
layered structure, referred to as a foliation, plays an essential role and
determines the mobility restrictions of the topological excitations. In this
work, we introduce a new kind of field theory to describe these phases: a
foliated field theory. We also introduce a new lattice model and
string-membrane-net condensation picture of these phases, which is analogous to
the string-net condensation picture of topological order.Comment: 22+15 pages, 8 figures; v3 added a summary of our model near the end
of the introductio
Foliated fracton order in the checkerboard model
In this work, we show that the checkerboard model exhibits the phenomenon of
foliated fracton order. We introduce a renormalization group transformation for
the model that utilizes toric code bilayers as an entanglement resource, and
show how to extend the model to general three-dimensional manifolds.
Furthermore, we use universal properties distilled from the structure of
fractional excitations and ground-state entanglement to characterize the
foliated fracton phase and find that it is the same as two copies of the X-cube
model. Indeed, we demonstrate that the checkerboard model can be transformed
into two copies of the X-cube model via an adiabatic deformation.Comment: 8 pages, 9 figure
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