SrMnSb 2 is suggested to be a magnetic topological semimetal. It contains square, 2D Sb planes with non-symmorphic crystal symmetries that could protect band crossings, offering the possibility of a quasi-2D, robust Dirac semi-metal in the form of a stable, bulk (3D) crystal. Here, we report a combined and comprehensive experimental and theoretical investigation of the electronic structure of SrMnSb 2 , including the first ARPES data on this compound. SrMnSb 2 possesses a small Fermi surface originating from highly 2D, sharp and linearly dispersing bands (the 'Y-states') around the (0,π/a)-point in kspace. The ARPES Fermi surface agrees perfectly with that from bulk-sensitive Shubnikov de Haas data from the same crystals, proving the Y-states to be responsible for electrical conductivity in SrMnSb 2 . DFT and tight binding (TB) methods are used to model the electronic states, and both show good agreement with the ARPES data. Despite the great promise of the latter, both theory approaches show the Y-states to be gapped above E F , suggesting trivial topology. Subsequent analysis within both theory approaches shows the Berry phase to be zero, indicating the non-topological character of the transport in SrMnSb 2 , a conclusion backed up by the analysis of the quantum oscillation data from our crystals.

Vanadium dioxide (VO 2 ) is a much-discussed material for oxide electronics and neuromorphic computing applications. Here, heteroepitaxy of VO 2 is realized on top of oxide nanosheets that cover either the amorphous silicon dioxide surfaces of Si substrates or X-ray transparent silicon nitride membranes. The out-of-plane orientation of the VO 2 thin films is controlled at will between (011) M1 /(110) R and (−402) M1 /(002) R by coating the bulk substrates with Ti 0.87 O 2 and NbWO 6 nanosheets, respectively, prior to VO 2 growth. Temperature-dependent X-ray diffraction and automated crystal orientation mapping in microprobe transmission electron microscope mode (ACOM-TEM) characterize the high phase purity, the crystallographic and orientational properties of the VO 2 films. Transport measurements and soft X-ray absorption in transmission are used to probe the VO 2 metal-insulator transition, showing results of a quality equal to those from epitaxial films on bulk single-crystal substrates. Successful local manipulation of two different VO 2 orientations on a single substrate is demonstrated using VO 2 grown on lithographically patterned lines of Ti 0.87 O 2 and NbWO 6 nanosheets investigated by electron backscatter diffraction. Finally, the excellent suitability of these nanosheet-templated VO 2 films for advanced lensless imaging of the metalinsulator transition using coherent soft X-rays is discussed.

PhySH: Complex oxides; transition metal oxides; X-ray absorption; X-ray magnetic circular dichroism; thin films; scanning transmission electron microscopy. Abstract We report charge-transfer up to a single electron per interfacial unit cell across non-polar heterointerfaces from the Mott insulator LaTiO 3 to the charge transfer insulator LaCoO 3 . In high-quality bi-and tri-layer systems grown using pulsed laser deposition, soft X-ray absorption, dichroism and STEM-EELS are used to probe the cobalt 3d-electron count and provide an element-specific investigation of the magnetic properties. The experiments prove a deterministically-tunable charge transfer process acting in the LaCoO 3 within three unit cells of the heterointerface, able to generate full conversion to 3d 7 divalent Co, which displays a paramagnetic ground state. The number of LaTiO 3 |LaCoO 3 interfaces, the thickness of an additional 'break' layer between the LaTiO 3 and LaCoO 3 , and the LaCoO 3 film thickness itself in tri-layers provide a trio of sensitive control knobs for the charge transfer process, illustrating the efficacy of O2p-band alignment as a guiding principle for property design in complex oxide heterointerfaces.

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