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  1. Abstract

    The shape of 3d-orbitals often governs the electronic and magnetic properties of correlated transition metal oxides. In the superconducting cuprates, the planar confinement of the$${d}_{{x}^{2}-{y}^{2}}$$dx2y2orbital dictates the two-dimensional nature of the unconventional superconductivity and a competing charge order. Achieving orbital-specific control of the electronic structure to allow coupling pathways across adjacent planes would enable direct assessment of the role of dimensionality in the intertwined orders. Using CuL3and PrM5resonant x-ray scattering and first-principles calculations, we report a highly correlated three-dimensional charge order in Pr-substituted YBa2Cu3O7, where the Prf-electrons create a direct orbital bridge between CuO2planes. With this we demonstrate that interplanar orbital engineering can be used to surgically control electronic phases in correlated oxides and other layered materials.

  2. Electrical resistivity measurements were performed on single crystals of URu2–xOsxSi2up tox= 0.28 under hydrostatic pressure up toP= 2 GPa. As the Os concentration,x, is increased, 1) the lattice expands, creating an effective negative chemical pressurePch(x); 2) the hidden-order (HO) phase is enhanced and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase; and 3) less external pressurePcis required to induce the HO→LMAFM phase transition. We compare the behavior of theT(x,P) phase boundary reported here for the URu2-xOsxSi2system with previous reports of enhanced HO in URu2Si2upon tuning withPor similarly in URu2–xFexSi2upon tuning with positivePch(x). It is noteworthy that pressure, Fe substitution, and Os substitution are the only known perturbations that enhance the HO phase and induce the first-order transition to the LMAFM phase in URu2Si2. We present a scenario in which the application of pressure or the isoelectronic substitution of Fe and Os ions for Ru results in an increase in the hybridization of the U-5f-electron and transition metald-electron states which leads to electronic instability in the paramagnetic phase and the concurrent formation of HO (and LMAFM) in URu2Si2. Calculations in the tight-binding approximation are included to determine the strength of hybridization between the U-5f-electron states and thed-electron states ofmore »Ru and its isoelectronic Fe and Os substituents in URu2Si2.

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