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Through the use of Heisenberg spin-spin interactions, we provide analytical representations for inelastic neutron scattering eigenstates and excitation cross sections of the general S1-S2 spin dimeric systems. Using an exact diagonalization approach to the spin Hamiltonian, we analyze various spin coefficients to provide general representations for the neutron scattering cross sections of two interacting spins. We also provide a generalized method for the determination of Sz-polarized excitations, which produces an approximation for the spin excitations within an applied z-axis magnetic field. These calculations enhance the general understanding of the interactions between two individual or compound spin systems, which can help provide insight into condensed matter systems such as molecular magnets, quantum dots, and spintronic systems, as well as particle physics investigations into quark matter and meson interactions. [ABSTRACT FROM AUTHOR]

Using polarized neutron reflectometry, we observe an induced magnetization of 75±25 kA/m at 10 K in a La0.7Sr0.3MnO3 (LSMO)/BiFeO3 superlattice extending from the interface through several atomic layers of the BiFeO3 (BFO). The induced magnetization in BFO is explained by density functional theory, where the size of band gap of BFO plays an important role. Considering a classical exchange field between the LSMO and BFO layers, we further show that magnetization is expected to extend throughout the BFO, which provides a theoretical explanation for the results of the neutron scattering experiment. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs>) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO3/ YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO3, we are able to show that a metallic ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interaction strengths, from the first-principles calculations, into a resultant generic phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the presence of a hysteresis loop in field-dependent magnetization data. The emergence of interfacial ferromagnetism should have implications to electronic and transport properties. [ABSTRACT FROM AUTHOR]

We combined Raman and infrared vibrational spectroscopies with complementary lattice dynamics calculations and magnetization measurements to reveal the dynamic aspects of charge-lattice-spin coupling in Co[N(CN)2]2. Our work uncovers electron-phonon coupling as a magnetic field-driven avoided crossing of the low-lying Co2+ electronic excitation with two ligand phonons and a magnetoelastic effect that signals a flexible local CoN6 environment. Their simultaneous presence indicates the ease with which energy is transferred over multiple length and time scales in this system. [ABSTRACT FROM AUTHOR]

We investigate the possibility of multiband superconductivity in SrTiO3 films and interfaces using a two-dimensional two-band model. In the undoped compound, one of the bands is occupied whereas the other is empty. As the chemical potential shifts due to doping by negative charge carriers or application of an electric field, the second band becomes occupied and gives rise to a strong enhancement of the transition temperature and a sharp feature in the gap functions, which is manifested in the local density of states spectrum. By comparing our results with tunneling experiments in Nb-doped SrTiO3, we find that intraband pairing dominates over interband pairing, unlike other known multiband superconductors. Given the similarities with the value of the transition temperature and with the band structure of LaAlO3/SrTiO3 heterostructures, we speculate that the superconductivity observed in SrTiO3 interfaces may be similar in nature to that of bulk SrTiO3, involving multiple bands with distinct electronic occupations. [ABSTRACT FROM AUTHOR]

We evaluate the spin-wave spectra for the high-field phases of the frustrated triangular lattice antiferromagnet with a focus on the observed high-magnetic-field phases of CuFe02. After determining the appropriate magnetic ground state using a combination of Monte Carlo simulations and variational methods for a two-dimensional triangular lattice, we evaluate the spin excitation frequencies and intensities using a rotational Holstein-Primakoff expansion for both the collinear and noncollinear states. These predictions should help experimentalists to identify the magnetic ground states of CuFe02 and other triangular-lattice antiferromagnets using inelastic neutron scattering. [ABSTRACT FROM AUTHOR]

Through an analysis and modeling of data from various experimental techniques, we present clear evidence for the presence of a hidden-order pseudogap in URu2Si2 in the temperature range 25-17.5 K. Considering fluctuations of the hidden-order energy gap at the transition, we evaluate the effects that gap fluctuations would produce on observables like tunneling conductance, neutron scattering, and nuclear resonance, and relate them to the experimental findings. We show that the transition into the hidden-order phase is likely second order and is preceded by the onset of noncoherent hidden-order fluctuations. [ABSTRACT FROM AUTHOR]

We examine the modified electronic states at the interface between superconducting and ferro(para)electric heterostructures. We find that electric polarization P and superconducting Ψ order parameters can be significantly modified due to coupling through linear terms brought about by explicit symmetry breaking at the interface. Using an effective action and a Ginzburg-Landau formalism, we show that an interaction term linear in the electric polarization will modify the superconducting order parameter ? at the interface. This also produces modulation of a ferroelectric polarization. It is shown that a paraelectric-superconductor interaction will produce an interface-induced polarization. [ABSTRACT FROM AUTHOR]

Interfaces between transition-metal oxides provide an intriguing platform for modifying the ground states of single constituent materials and creating desired functionalities for applications in oxide-based electronics. Here, we demonstrate that the metallic and ferromagnetic responses of La0.7Sr0.3MnO3 (LSMO) films with thicknesses less than 4 nm, which are insulating when grown directly on SrTiO3 substrates, can be restored through interfacing with a high-temperature cuprate superconductor EuBa2Cu3O7-δ (EBCO). We carried out scanning tunneling microscopy and spectroscopy measurements on the electronic structure of LSMO/EBCO bilayers with thickness of LSMO layer varying from 2 to 7 nm. Our results suggest that the transfer of holes from EBCO to LSMO, caused by the difference in their work functions, is responsible for driving LSMO film with thickness of only five unit cells to the metallic state. [ABSTRACT FROM AUTHOR]

We bring together optical spectroscopy and first-principles calculations to reveal the electronic properties of the chiral ferromagnet Fe1/3TaS2. Signatures of chirality are superimposed upon a complex free-carrier response that emanates from both Ta and Fe bands. These include a honeycomb charge density pattern in the Fe layer and a hole → electron pocket crossover at the K point, low-energy excitations between spin split bands that cross the Fermi surface, and clustered rather than well-separated on-site and charge-transfer excitations. These findings advance the understanding of intercalation and symmetry breaking on the fundamental excitations in metallic chalcogenides. [ABSTRACT FROM AUTHOR]