Bias-Free Access to Orbital Angular Momentum in Two-Dimensional Quantum Materials.

The demonstration of a topological band inversion constitutes the most elementary proof of a quantum spin Hall insulator (QSHI). On a fundamental level, such an inverted band gap is intrinsically related to the bulk Berry curvature, a gauge-invariant fingerprint of the wave function's quantum geometric properties in Hilbert space. Intimately tied to orbital angular momentum (OAM), the Berry curvature can be, in principle, extracted from circular dichroism in angle-resolved photoemission spectroscopy (CD-ARPES), were it not for interfering final state photoelectron emission channels that obscure the initial state OAM signature. Here, we outline a full-experimental strategy to avoid such interference artifacts and isolate the clean OAM from the CD-ARPES response. Bench-marking this strategy for the recently discovered atomic monolayer system indenene, we demonstrate its distinct QSHI character and establish CD-ARPES as a scalable bulk probe to experimentally classify the topology of two-dimensional quantum materials with time reversal symmetry.

Achieving environmental stability in an atomically thin quantum spin Hall insulator via graphene intercalation.

Atomic monolayers on semiconductor surfaces represent an emerging class of functional quantum materials in the two-dimensional limit - ranging from superconductors and Mott insulators to ferroelectrics and quantum spin Hall insulators. Indenene, a triangular monolayer of indium with a gap of ~ 120 meV is a quantum spin Hall insulator whose micron-scale epitaxial growth on SiC(0001) makes it technologically relevant. However, its suitability for room-temperature spintronics is challenged by the instability of its topological character in air. It is imperative to develop a strategy to protect the topological nature of indenene during ex situ processing and device fabrication. Here we show that intercalation of indenene into epitaxial graphene provides effective protection from the oxidising environment, while preserving an intact topological character. Our approach opens a rich realm of ex situ experimental opportunities, priming monolayer quantum spin Hall insulators for realistic device fabrication and access to topologically protected edge channels.

Design and realization of topological Dirac fermions on a triangular lattice.

Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. Key to engineer the topologically non-trivial band ordering and sizable band gaps is strong spin-orbit interaction. Following Kane and Mele's original suggestion, one approach is to synthesize monolayers of heavy atoms with honeycomb coordination accommodated on templates with hexagonal symmetry. Yet, in the majority of cases, this recipe leads to triangular lattices, typically hosting metals or trivial insulators. Here, we conceive and realize "indenene", a triangular monolayer of indium on SiC exhibiting non-trivial valley physics driven by local spin-orbit coupling, which prevails over inversion-symmetry breaking terms. By means of tunneling microscopy of the 2D bulk we identify the quantum spin Hall phase of this triangular lattice and unveil how a hidden honeycomb connectivity emerges from interference patterns in Bloch px ± ipy-derived wave functions.

[13-year old girl with fever 6 months after returning from sub-Saharan Africa]. / Rezidivierende Fieberschübe 6 Monate nach Afrikareise - Fall 4 / 2015.

HISTORY AND ADMISSION FINDINGS: A 13-year-old girl presented with regular fevers, 6 months after a prolonged trip through Africa. The patient reported relapsing fevers at 48 hour intervals. Each febrile episode was followed by pronounced fatigue and a subsequent recovery back to her usual state of health. She reported having taken weekly mefloquine during and after the trip to Africa. INVESTIGATIONS: Labortory evaluation revealed a hemoltytic anemia (hemoglobin: 10.8 g / dl, normal range: 12.3-16.0; haptoglobin: < 13 mg / dl, normal range 38-205). An abdominal ultrasound showed a marked splenomegaly (diameter: > 13.1 cm). DIAGNOSIS, TREATMENT AND COURSE: A peripheral blood film showed Plasmodium parasites with marked stippling. PCR and sequenicing of the ribosomal RNA gene identified Plasmodium ovale. The patient responded well to oral chloroquine therapy and laboratory parameters normalized within 8 days. After determination of a normal glucose-6-phosphate dehydrogenase activity a 2-week-long therapy with primaquine was initiated (0,3 mg / kg per kg bodyweight of primaquine base daily for 14 days) to eliminate the hyponozoite stage of the parasite. CONCLUSIONS: Currently used prophylacic agents against Malaria (mefloquine, atovaquone / proguanil hydrochloride, doxyxycline) do not prevent chronic liver stage infection (hypnozoite stage) with Plasmodium ovale or Plasmodium vivax. After chemoprophylaxis tertian malaria due Plasmodium vivax or Plasmodium ovale can occur. Therefore, tertian malaria should always be considered in febrile individuals who returned from a trip to the tropics even if chemoprophylaxis was taken.