Antiferromagnetic MnNi tips for spin-polarized scanning probe microscopy

Spin-polarized scanning tunneling microscopy (SP-STM) measures tunnel magnetoresistance (TMR) with atomic resolution. While various methods for achieving SP probes have been developed, each is limited with respect to fabrication, performance, and allowed operating conditions. In this study, we present the fabrication and use of SP-STM tips made from commercially available antiferromagnetic $\rm{Mn_{88}Ni_{12}}$ foil. The tips are intrinsically SP, which is attractive for exploring magnetic phenomena in the zero field limit. The tip material is relatively ductile and straightforward to etch. We benchmark the conventional STM and spectroscopic performance of our tips and demonstrate their spin sensitivity by measuring the two-state switching of holmium single atom magnets on MgO/Ag(100)

Spontaneous exciton condensation in 1T-TiSe2: a BCS-like approach

Recently strong evidence has been found in favor of a BCS-like condensation of excitons in 1\textit{T}-TiSe$_2$. Theoretical photoemission intensity maps have been generated by the spectral function calculated within the excitonic condensate phase model and set against experimental angle-resolved photoemission spectroscopy data. Here, the calculations in the framework of this model are presented in detail. They represent an extension of the original excitonic insulator phase model of J\'erome \textit{et al.} [Phys. Rev. {\bf 158}, 462 (1967)] to three dimensional and anisotropic band dispersions. A detailed analysis of its properties and further comparison with experiment are also discussedComment: Submitted to PRB, 11 pages, 7 figure

The electronic structure of La1−x_{1-x}Srx_{x}MnO3_{3} thin films and its TcT_c dependence as studied by angle-resolved photoemission

We present angle-resolved photoemission spectroscopy results for thin films of the three-dimensional manganese perovskite La$_{1-x}$Sr$_{x}$MnO$_{3}$. We show that the transition temperature ($T_c$) from the paramagnetic insulating to ferromagnetic metallic state is closely related to details of the electronic structure, particularly to the spectral weight at the ${\bf k}$-point, where the sharpest step at the Fermi level was observed. We found that this ${\bf k}$-point is the same for all the samples, despite their different $T_c$. The change of $T_c$ is discussed in terms of kinetic energy optimization. Our ARPES results suggest that the change of the electronic structure for the samples having different transition temperatures is different from the rigid band shift.Comment: Accepted by Journal of Physics: Condensed Matte

Bulk electronic structure of superconducting LaRu2P2 single crystals measured by soft x-ray angle-resolved photoemission spectroscopy

We present a soft X-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it is significantly different from its counterpart in high-temperature superconducting Fe-pnictides. In particular the bandwidth renormalization present in the Fe-pnictides (~2 - 3) is negligible in LaRu2P2 even though the mass enhancement is similar in both systems. Our results suggest that the superconductivity in LaRu2P2 has a different origin with respect to the iron pnictides. Finally we demonstrate that the increased probing depth of SX-ARPES, compared to the widely used ultraviolet ARPES, is essential in determining the bulk electronic structure in the experiment.Comment: 4 pages, 4 figures, 1 supplemental material. Accepted for publication in Physical Review Letter

The Role of Lattice Coupling in Establishing Electronic and Magnetic Properties in Quasi-One-Dimensional Cuprates

High resolution resonant inelastic x-ray scattering has been performed to reveal the role of lattice-coupling in a family of quasi-1D insulating cuprates, Ca$_{2+5x}$Y$_{2-5x}$Cu$_5$O$_{10}$. Site-dependent low energy excitations arising from progressive emissions of a 70 meV lattice vibrational mode are resolved for the first time, providing a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intra-chain spin exchange interactions. Our results indicate that the lattice degrees of freedom are fully integrated into the electronic behavior in low dimensional systems.Comment: 5 pages, 4 figur

The hard X-ray Photon Single-Shot Spectrometer of SwissFEL - Initial characterization

SwissFEL requires the monitoring of the photon spectral distribution at a repetition rate of 100 Hz for machine optimization and experiment online diagnostics. The Photon Single Shot Spectrometer has been designed for the photon energy range of 4 keV to 12 keV provided by the Aramis beamline. It is capable of measuring the spectrum in a non-destructive manner, with an energy resolution of Δ E/E = (2-5) × 10-5 over a bandwidth of 0.5% on a shot-to-shot basis. This article gives a detailed description about the technical challenges, structures, and considerations when building such a device, and to further enhance the performance of the spectrometer

Angle-scanned photoemission: Fermi surface mapping and structural determination

A brief survey of the angle-scanned photoemission technique is given. It incorporates two complementary methods in one:http://www.sciencedirect.com/science/article/B6TVX-3X82696-4F/1/e2ffd4efc660238ad8d4ad8f685991b