Articles in 2020

Recently, Nb-doping of topological insulator Bi₂Se₃ has attracted much attention as a way to pursue topological superconductivity. Here, in contrast to previous reports, superconductivity in Nb_xBi₂Se₃ is found to arise from the misfit phase (BiSe)_1.10NbSe₂ and not from Nb intercalation into Bi₂Se₃.

Perovskite nanocrystals are promising for use in light emitting diodes, but improved hole injection is needed. Here, MoO₃ is added as an electric dipole layer between hole injection and transport layers, achieving a current efficiency of 72.7cd/A in a green light emitting diode.

Knowing the atomic structure of liquid iron oxide is key to understanding steelmaking processes and magma flows. Here, Fe-O atomic coordination numbers are determined during levitation melting at a range of temperatures and oxygen partial pressures, revealing low coordination numbers.

Anion-exchange doping allows high carrier densities in organic semiconductors but can be limited by host-guest steric effects. Here, these are analyzed, and high doping efficiency is realized for a specific combination of a polymer with sparse side-chains and a large dopant, forming a close-packed structure.

Coupling of semiconductor quantum wells is governed by short-range interactions, and thus limited to distances of roughly 10 nm. Here, magnetically controlled energy transfer between quantum wells over a distance of 2.15 μm is achieved via polariton-mediated coupling.

The hierarchical structure of nacre is known to contribute to its high strength and toughness, providing inspiration for many biomimetic materials. Here, co-oriented 20 µm stacks of aragonite platelets are shown to contribute to the toughness of nacre, defining a new characteristic length scale.

In nonlinear optics, efficient frequency conversion typically requires phase-matching conditions, resulting in wavelength, polarization, and angular selectivity. Here, these constraints are overcome in a supercrystal with giant refraction index, allowing wide spectral and angular acceptance.

Multiferroics that are both ferroelectric and ferromagnetic are highly desirable for technological applications but extremely rare. Here, signatures of a ferroelectric phase transition, supported by theoretical calculations, are observed in ferromagnetic EuO under a large epitaxial strain of 6.4%.

Materials with a large spin-Hall effect are highly desirable for spintronic devices. Here, non-equilibrium thin film synthesis is used to fabricate copper-iridium binary alloys beyond their solubility limit, achieving a large spin-Hall angle of approximately 6% in Cu₇₆Ir₂₄.

The discovery of new alloys with desirable mechanical properties is traditionally a time consuming process. Here, machine learning is applied to the discovery of aluminum alloys, revealing a compositionally-lean alloy with an ultimate tensile strength of 952 MPa and 6.3% elongation.

Architectured materials are known for their mechanical properties, yet the addition of other functional properties would widen their applications range. Here, hydrophobicity is imparted to a high-strength carbon microlattice via a hierarchical nanographitic skin by rapid joule heating.

Strong piezoelectricity is typically due to reorientation of ferroelectric domains and is not expected in cubic systems. Here, the strong piezoelectricity of pseudo-cubic 0.3BaTiO₃–0.1Bi(Mg_1/2Ti_1/2)O₃–0.6BiFeO₃ is explained in terms of partial ordering of Bi ions adapted to any applied field direction.

Replacing metal electrodes in lithium-ion batteries with organic materials reduces environmental impact and might lead to high gravimetric capacity. Here, organic electrodes containing a naphthazarin-dimer skeleton achieve an initial capacity of 416 mAh g⁻¹ and energy density of 1.1 Wh g⁻¹ in a lithium-ion battery.

Atomic processes on the surface of a catalyst control reaction mechanisms. Here, in-situ imaging of manganese adatom dynamics on La_0.6Sr_0.4MnO₃ and Pr_0.67Ca_0.33MnO₃ surfaces used in the oxygen evolution reaction reveals the importance of partial surface solvation of active metal sites on reaction mechanism.

Aligning cholesteric liquid crystal nanorods is key to their optical properties, yet challenging to achieve in artificial systems. Here cellulose nanorods are fractionated from suspension, revealing that nanorod length correlates with helical twist, allowing uniformly violet films to be created.

Robotic devices that can actuate at high speeds are challenging to achieve. Here, soft robotic devices driven by low magnetic fields show large deformations at frequencies of up to 100 Hz and are capable of a range of motions, including cross-clapping, walking, swimming and closing around a living fly.

The chemical pathways by which photocatalytic hydrogen production occurs remain to be fully understood. Here, a model system is studied, composed of single atoms deposited on quantum dots, attached to a primary photocatalyst.

Deep vein thrombosis is the clotting of blood in deep veins. Here, a microfluidic device containing flexible valves fabricated in-situ is used to investigate the effects of blood flow conditions and valve elasticity on thrombus formation, revealing the circumstance under which clotting occurs.

Hydrophobic coatings are increasingly important in modern technology, but hard to study in the extreme non-wetting limit. Here, micropipette force sensors can directly measure nN-scale friction forces and, combined with particle image velocimetry, reveal pure rolling dynamics of slow water droplets.

Intermediate band solar cells have the ability to reach efficiencies similar to multijunction cells using a single semiconductor junction. Here, enhanced two-photon carrier generation is demonstrated on a silicon substrate in an InGaN/GaN quantum dot-in-nanowire heterostructure intermediate band solar cell.