Physicians’ Participation in ACOs is Lower in Places With Vulnerable Populations Than in More Affluent Communities

In 2013, physician participation in accountable care organizations (ACOs) was inversely related to the percentage of the local population that was black, living in poverty, uninsured, or disabled or that had less than a high school education. This risks exacerbating disparities in the quality of care received by these vulnerable populations

Renormalized Classical Theory of Quantum Magnets

We derive a renormalized classical spin (RCS) theory for $S > 1/2$ quantum magnets by constraining a generalized classical theory that includes all multipolar fluctuations to a reduced CP$^1$ phase space of dipolar SU($2$) coherent states. When the spin Hamiltonian $\hat{\cal{H}}^{S}$ is linear in the spin operators $\hat{\boldsymbol{S}}_j$ for each lattice site $j$, the RCS Hamiltonian $\tilde{\cal{H}}_{\rm cl}$ coincides with the usual classical model $\cal{H}_{\rm cl} = \lim_{S\rightarrow\infty} \hat{\cal{H}}^S$. In the presence of non-linear terms, however, the RCS theory is more accurate than $\cal{H}_{\rm cl}$. For the many materials modeled by spin Hamiltonians with (non-linear) single-ion anisotropy terms, the use of the RCS theory is essential to accurately model phase diagrams and to extract the correct Hamiltonian parameters from neutron scattering dataComment: 5 pages, 1 figure

Interplay Between Magnetic Frustration and Quantum Criticality in the Unconventional Ladder Antiferromagnet C9H18N2CuBr4

Quantum fluctuation in frustrated magnets and quantum criticality at the transition between different quantum phases of matter are two of the cornerstones in condensed matter physics. Here we demonstrate the nontrivial interplay between them in the spin-1/2 coupled two-leg ladder antiferromagnet C9H18N2CuBr4. Employing the high-resolution neutron spectroscopy, we unambiguously identify a weakly first-order hydrostatic pressure-driven quantum phase transition, which arises from fluctuations enhanced by the frustrating interlayer coupling. An exotic pressure-induced quantum disordered state is evidenced by the broad spectral linewidth observed near the phase transition. Interestingly, we find that the gapped transverse excitations in the Neel-ordered phase at ambient pressure cannot be described by the conventional S=1 magnons, i.e., the spin wave quanta, associated with explicit symmetry breaking, and thus the three-dimensional magnetic order ought to emerge in an unconventional way. We further apply the quantum Fisher information to show the presence of bipartite entanglement at criticality at least up to 1.1 K in the same material.Comment: 10 pages and 6 figures. We call for theoretical understanding of the nontrivial interplay observed in this materia

Size dependence of the photoinduced magnetism and long-range ordering in Prussian blue analog nanoparticles of rubidium cobalt hexacyanoferrate

Nanoparticles of rubidium cobalt hexacyanoferrate (Rb$_j$Co$_k$[Fe(CN)$_6$]$_l \cdot n$H$_2$O) were synthesized using different concentrations of the polyvinylpyrrolidone (PVP) to produce four different batches of particles with characteristic diameters ranging from 3 to 13 nm. Upon illumination with white light at 5 K, the magnetization of these particles increases. The long-range ferrimagnetic ordering temperatures and the coercive fields evolve with nanoparticle size. At 2 K, particles with diameters less than approximately 10 nm provide a Curie-like magnetic signal.Comment: 10 pages, 6 figures in text, expanded text and dat