L. Dudy

Bismuthene on a SiC substrate: A candidate for a high-temperature quantum spin Hall material

Making a large-gap topological insulator Although of interest to basic research, topological insulators (TIs) have not yet lived up to their technological potential. This is partly because their protected surface-edge state usually lives within a narrow energy gap, with its exotic transport properties overwhelmed by the ordinary bulk material. Reis et al. show that a judicious choice of materials can make the gap wide enough for the topological properties to be apparent at room temperature. Numerical calculations indicate that a monolayer of Bismuth grown on SiC(0001) is a two-dimensional TI with a large energy gap. The researchers fabricated such a heterostructure and characterized it using scanning tunneling spectroscopy. The size of the experimentally measured gap was consistent with the calculations. Science, this issue p. 287 Scanning tunneling spectroscopy indicates a large energy gap and conducting edge states, consistent with calculations. Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high–atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron volt and conductive edge states consistent with theory. Our combined theoretical and experimental results demonstrate a concept for a quantum spin Hall wide-gap scenario, where the chemical potential resides in the global system gap, ensuring robust edge conductance.

Elemental topological insulator with tunable Fermi level: strained α-Sn on InSb(001).

We report on the epitaxial fabrication and electronic properties of a topological phase in strained α-Sn on InSb. The topological surface state forms in the presence of an unusual band order not based on direct spin-orbit coupling, as shown in density functional and GW slab-layer calculations. Angle-resolved photoemission including spin detection probes experimentally how the topological spin-polarized state emerges from the second bulk valence band. Moreover, we demonstrate the precise control of the Fermi level by dopants.

In Situ Control of Separate Electronic Phases on SrTiO3 Surfaces by Oxygen Dosing

Insulating SrTiO3 (STO) can host 2D electron systems (2DESs) on its surfaces, caused by oxygen defects. This study shows that the STO surface exhibits phase separation once the 2DES is formed and relates this inhomogeneity to recently reported magnetic order at STO surfaces and interfaces. The results open pathways to exploit oxygen defects for engineering the electronic and magnetic properties of oxides.

Microscopic origin of the mobility enhancement at a spinel/perovskite oxide heterointerface revealed by photoemission spectroscopy

The spinel/perovskite heterointerface

Topological surface state of α−Sn on InSb(001) as studied by photoemission

\ensuremath{\gamma}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}/{\mathrm{SrTiO}}_{3}

Double band inversion in α -Sn: Appearance of topological surface states and the role of orbital composition

hosts a two-dimensional electron system (2DES) with electron mobilities exceeding those in its all-perovskite counterpart

Tailoring Materials for Mottronics: Excess Oxygen Doping of a Prototypical Mott Insulator

{\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}

Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

by more than an order of magnitude, despite the abundance of oxygen vacancies which act as electron donors as well as scattering sites. By means of resonant soft x-ray photoemission spectroscopy and ab initio calculations, we reveal the presence of a sharply localized type of oxygen vacancies at the very interface due to the local breaking of the perovskite symmetry. We explain the extraordinarily high mobilities by reduced scattering resulting from the preferential formation of interfacial oxygen vacancies and spatial separation of the resulting 2DES in deeper

Disentangling specific versus generic doping mechanisms in oxide heterointerfaces

{\mathrm{SrTiO}}_{3}

Atomic-Scale Mapping of Layer-by-Layer Hydrogen Etching and Passivation of SiC(0001) Substrates

layers. Our findings comply with transport studies and pave the way towards defect engineering at interfaces of oxides with different crystal structures.