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Carrier-controlled anomalous Hall effect in an intrinsic ferromagnetic semiconductor
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Mott transition controlled by lattice-orbital coupling in 3 d -metal-doped double-layer ruthenates
We have investigated unusual phase transitions that were triggered by chemical doping in Ca 3 Ru 2 O 7 . Our experiments showed that doping with a few percent of Mn (>4%) can change the quasi-two-dimensional metallic state of Ca 3 Ru 2 O 7 into a Mott insulating state with a G-type antiferromagnetic order, but this Mott state cannot be induced by Fe doping. By combining these results with first-principles calculations, we show that lattice-orbital coupling (LOC) plays an important role in the Mott transition. Interestingly, the transition temperature T MIT is found to be predetermined by a structural parameter denoted by c/√ab at temperatures far above Néel temperature T N . This LOC-assisted Mott transition clearly contrasts with the band-filling picture. It is addressed that this type of Mott transition originates in the strong scattering centers formed by specific 3d dopants. The dopant-scattering picture is then applied to explain the puzzling doping effects that occur in other ruthenates and 3d oxides. As a result, our findings will advance the general understanding of how the unusual properties of 4d correlated systems are governed by the complex interplay that occurs among the charge, spin, lattice, and orbital degrees of freedom.
Modeling of the gate-controlled Kondo effect at carbon point defects in graphene
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Nonlinear phononic control and emergent magnetism in Mott insulating titanates
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Competition between orthorhombic and re-entrant tetragonal phases in underdoped Ba 1–x K x Fe 2 As 2 probed by the response to controlled disorder
Low-temperature (22 K) irradiation with 2.5-MeV electrons, creating point defects affecting elastic scattering, was used to study the competition between stripe C 2 and tetragonal C 4 antiferromagnetic phases which exist in a narrow doping range around x = 0.25 in hole-doped Ba 1–x K x Fe 2 As 2 . In nearby compositions outside of this range, at x = 0.22 and x = 0.19, the temperatures of both the concomitant orthorhombic/stripe antiferromagnetic transition T C2 and the superconducting transition T c are monotonically suppressed by added disorder at similar rates of about 0.1 K/ μ Ωcm, as revealed through using resistivity variation as an intrinsic measure of scattering rate. In a stark contrast, a rapid suppression of the C 4 phase at the rate of 0.24 K/ μ Ωcm is found at x = 0.25. Moreover, this suppression of the C 4 phase is accompanied by unusual disorder-induced stabilization of the C 2 phase, determined by resistivity and specific heat measurements. Furthermore, the rate of the C 4 phase suppression is notably higher than the suppression rate of the spin-vortex phase in the Ni-doped CaKFe 4 As 4 (0.16 K/ μ Ωcm).
Controlling excited-state contamination in nucleon matrix elements
We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a 2+1-flavor ensemble with lattices of size 32 3 × 64 generated using the rational hybrid Monte Carlo algorithm at 𝑎 = 0.081 fm and with 𝑀 𝜋 = 312 MeV. The statistical precision of the data is improved using the all-mode-averaging method. We compare two methods for reducing excited-state contamination: a variational analysis and a 2-state fit to data at multiple values of the source-sink separation 𝑡 sep . We show that both methods can be tuned to significantly reduce excited-state contamination and discuss their relative advantages and cost effectiveness. Here a detailed analysis of the size of source smearing used in the calculation of quark propagators and the range of values of 𝑡 sep needed to demonstrate convergence of the isovector charges of the nucleon to the 𝑡 sep → ∞ estimates is presented.
Multiband Optical Absorption Controlled by Lattice Strain in Thin-Film LaCrO 3
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Viscosity Control of the Dynamic Self-Assembly in Ferromagnetic Suspensions
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Precision Control of the Electron Longitudinal Bunch Shape Using an Emittance-Exchange Beam Line
We report on the experimental generation of relativistic electron bunches with a tunable longitudinal bunch shape. A longitudinal bunch-shaping (LBS) beam line, consisting of a transverse mask followed by a transverse-to-longitudinal emittance exchange (EEX) beam line, is used to tailor the longitudinal bunch shape (or current profile) of the electron bunch. The mask shapes the bunch’s horizontal profile, and the EEX beam line converts it to a corresponding longitudinal profile. The Argonne wakefield accelerator rf photoinjector delivers electron bunches into a LBS beamline to generate a variety of longitudinal bunch shapes. The quality of the longitudinal bunch shape is limited by various perturbations in the exchange process. We develop a simple method, based on the incident slope of the bunch, to significantly suppress the perturbations
Parity-Controlled 2 π Josephson Effect Mediated by Majorana Kramers Pairs
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