Molecular Order Induced Charge Transfer in a C-Topological Insulator Moiré Heterostructure.

We synthesized and spectroscopically investigated monolayer (ML) C on the topological insulator (TI) BiTe. This C/BiTe heterostructure is characterized by an excellent translational order in a novel (4 × 4) C superstructure on a (9 × 9) cell of BiTe. Angle-resolved photoemission spectroscopy (ARPES) of C/BiTe reveals that ML C accepts electrons from the TI at room temperature, but no charge transfer occurs at low temperatures.

Exceptional behavior of a high-temperature superconductor in proximity to a ferromagnet in a bilayer film, LaSrMnO/YBaCuO.

We studied the electronic properties of a high-temperature superconductor in proximity to a ferromagnetic material in a bilayer film of LaSrMnO (LSMO)/YBaCuO (YBCO). High-quality single-crystalline films of YBCO and LSMO/YBCO were grown epitaxially on an SrTiO (001) surface. Magnetization data of the LSMO/YBCO bilayer exhibit ferromagnetic transition at about 255 K, which is much smaller than the Curie temperature of bulk LSMO.

Layer-resolved electronic behavior in a Kondo lattice system, CeAgAs.

We investigate the electronic structure of an antiferromagnetic Kondo lattice system CeAgAsemploying hard-ray photoemission spectroscopy. CeAgAs, an orthorhombic variant of HfCuSistructure, exhibits antiferromagnetic ground state, Kondo like resistivity upturn and compensation of magnetic moments at low temperatures. The photoemission spectra obtained at different photon energies suggest termination of the cleaved surface at cis-trans-As layers.

Evolution of local structure and superconductivity in CaFeAs.

We investigate the evolution of the local structural parameters and their implication in unconventional superconductivity of 122 class of materials employing extended x-ray absorption fine structure studies. The spectral functions near the Fe- and As-absorption edges of CaFeAsand its superconducting composition, CaFeCoAs(= 12 K) exhibit evidence of enhancement of Fe contributions near the Fermi level with Co substitution, which becomes more prominent at low temperatures indicating enhanced role of Fe in the electronic properties with doping. As-Fe and Fe-Fe bondlengths derived from the experimental data reveal evolution with temperature across the magneto-structural transition in the parent compound.

On-Demand Local Modification of High-T Superconductivity in Few Unit-Cell Thick Bi Sr CaCu O.

High-temperature superconductors (HTSs) are important for potential applications and for understanding the origin of strong correlations. Bi Sr CaCu O (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit-cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science.

Complex hybridization physics in CaFeAs- a high resolution hard x-ray photoemission study.

Employing high resolution hard x-ray photoemission spectroscopy, we investigate the electronic structure of an exotic Fe-based superconductor, CaFeAs, which exhibits rich temperature pressure phase diagram and dichotomy on achieving superconductivity on application of pressure. The experimental valence band spectra exhibit significant differences for experiments at different surface sensitivities. We discover that the change in angle between light polarization and surface normal leads to similar orbital selective spectral response suggesting requirement of different methodology to probe the surface-bulk differences.