High-efficiency and thermally stable FACsPbI perovskite photovoltaics.

α-FACsPbI is a promising absorbent material for efficient and stable perovskite solar cells (PSCs). However, the most efficient α-FACsPbI PSCs require the inclusion of the additive methylammonium chloride, which generates volatile organic residues (methylammonium) that limit device stability at elevated temperatures. Previously, the highest certified power-conversion efficiency of α-FACsPbI PSCs without methylammonium chloride was only approximately 24% (refs.

Recent Progress in Additive Manufacturing of Alloys and Composites.

Additive manufacturing, commonly referred to as 3D printing, is a fabrication method characterized by a layer-by-layer deposition process [...

The discovery of three-dimensional Van Hove singularity.

Arising from the extreme/saddle point in electronic bands, Van Hove singularity (VHS) manifests divergent density of states (DOS) and induces various new states of matter such as unconventional superconductivity. VHS is believed to exist in one and two dimensions, but rarely found in three dimension (3D). Here, we report the discovery of 3D VHS in a topological magnet EuCdAs by magneto-infrared spectroscopy.

Progress on the antiferromagnetic topological insulator MnBiTe.

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed matter physics. They represent a new class of materials exhibiting nontrivial topological phases, and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous Hall effect and the quantum spin Hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic orders.

Broad and colossal edge supercurrent in Dirac semimetal CdAs Josephson junctions.

Edge supercurrent has attracted great interest recently due to its crucial role in achieving and manipulating topological superconducting states. Proximity-induced superconductivity has been realized in quantum Hall and quantum spin Hall edge states, as well as in higher-order topological hinge states. Non-Hermitian skin effect, the aggregation of non-Bloch eigenstates at open boundaries, promises an abnormal edge channel.

Tautomeric mixture coordination enables efficient lead-free perovskite LEDs.

Lead halide perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable optoelectronic performance. However, there are potential toxicity issues with lead and removing lead from the best-performing PeLEDs-without compromising their high external quantum efficiencies-remains a challenge. Here we report a tautomeric-mixture-coordination-induced electron localization strategy to stabilize the lead-free tin perovskite TEASnI (TEAI is 2-thiopheneethylammonium iodide) by incorporating cyanuric acid.

Programming Crystallographic Orientation in Additive-Manufactured Beta-Type Titanium Alloy.

Additively manufactured metallic materials typically exhibit preferential <001> or <110> crystallographic orientations along the build direction. Nowadays, the challenge is to program crystallographic orientation along arbitrary 3D direction in additive-manufactured materials. In this work, it is established a technique of multitrack coupled directional solidification (MTCDS) to program the <001> crystallographic orientation along an arbitrary 3D direction in biomedical beta-type Ti-Nb-Zr-Ta alloys via laser powder bed fusion (LPBF).

Ion-Dipole Interaction Enabling Highly Efficient CsPbI Perovskite Indoor Photovoltaics.

Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) because of their easy-to-adjust bandgaps, which can be designed to cover the spectrum of any artificial light source. However, the serious non-radiative carrier recombination under low light illumination restrains the application of perovskite-based IPVs (PIPVs). Herein, polar molecules of amino naphthalene sulfonates are employed to functionalize the TiO substrate, anchoring the CsPbI perovskite crystal grains with a strong ion-dipole interaction between the molecule-level polar interlayer and the ionic perovskite film.

Giant nonlocal edge conduction in the axion insulator state of MnBiTe.

The recently discovered antiferromagnetic (AFM) topological insulator (TI) MnBiTe represents a versatile material platform for exploring exotic topological quantum phenomena in nanoscale devices. It has been proposed that even-septuple-layer (even-SL) MnBiTe can host helical hinge currents with unique nonlocal behavior, but experimental confirmation is still lacking. In this work, we report transport studies of exfoliated MnBiTe flakes with varied thicknesses down to the few-nanometer regime.

All-electrical switching of a topological non-collinear antiferromagnet at room temperature.

Non-collinear antiferromagnetic Weyl semimetals, combining the advantages of a zero stray field and ultrafast spin dynamics, as well as a large anomalous Hall effect and the chiral anomaly of Weyl fermions, have attracted extensive interest. However, the all-electrical control of such systems at room temperature, a crucial step toward practical application, has not been reported. Here, using a small writing current density of around 5 × 10 A·cm, we realize the all-electrical current-induced deterministic switching of the non-collinear antiferromagnet MnSn, with a strong readout signal at room temperature in the Si/SiO/MnSn/AlO structure, and without external magnetic field or injected spin current.

Additive Manufacturing of Alloys and Composites.

The emergence and development of high-performance materials have benefited from the revolution in modern manufacturing technology, in which additive manufacturing (AM) is the most representative over the last four decades [...

Topological Lifshitz transition and one-dimensional Weyl mode in HfTe.

Landau band crossings typically stem from the intra-band evolution of electronic states in magnetic fields and enhance the interaction effect in their vicinity. Here in the extreme quantum limit of topological insulator HfTe, we report the observation of a topological Lifshitz transition from inter-band Landau level crossings using magneto-infrared spectroscopy. By tracking the Landau level transitions, we demonstrate that band inversion drives the zeroth Landau bands to cross with each other after 4.

Tunable quantum gaps to decouple carrier and phonon transport leading to high-performance thermoelectrics.

Thermoelectrics enable direct heat-to-electricity transformation, but their performance has so far been restricted by the closely coupled carrier and phonon transport. Here, we demonstrate that the quantum gaps, a class of planar defects characterized by nano-sized potential wells, can decouple carrier and phonon transport by selectively scattering phonons while allowing carriers to pass effectively. We choose the van der Waals gap in GeTe-based materials as a representative example of the quantum gap to illustrate the decoupling mechanism.

Antisymmetric Seebeck Effect in a Tilted Weyl Semimetal.

Tilting the Weyl cone breaks the Lorentz invariance and enriches the Weyl physics. Here, we report the observation of a magnetic-field-antisymmetric Seebeck effect in a tilted Weyl semimetal, Co_{3}Sn_{2}S_{2}. Moreover, it is found that the Seebeck effect and the Nernst effect are antisymmetric in both the in-plane magnetic field and the magnetization.

Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators.

The layer Hall effect describes electrons spontaneously deflected to opposite sides at different layers, which has been experimentally reported in the MnBiTe thin films under perpendicular electric fields. Here, we reveal a universal origin of the layer Hall effect in terms of the so-called hidden Berry curvature, as well as material design principles. Hence, it gives rise to zero Berry curvature in momentum space but non-zero layer-locked hidden Berry curvature in real space.

Topological charge-entropy scaling in kagome Chern magnet TbMnSn.

In ordinary materials, electrons conduct both electricity and heat, where their charge-entropy relations observe the Mott formula and the Wiedemann-Franz law. In topological quantum materials, the transverse motion of relativistic electrons can be strongly affected by the quantum field arising around the topological fermions, where a simple model description of their charge-entropy relations remains elusive. Here we report the topological charge-entropy scaling in the kagome Chern magnet TbMnSn, featuring pristine Mn kagome lattices with strong out-of-plane magnetization.

Phase transitions in intrinsic magnetic topological insulator with high-frequency pumping.

In this work, we investigate the topological phase transitions in an effective model for a topological thin film with high-frequency pumping. In particular, our results show that the circularly polarized light can break the time-reversal symmetry and induce the quantum anomalous Hall insulator (QAHI) phase. Meanwhile, the bulk magnetic moment can also break the time-reversal symmetry.

Conformal quantum dot-SnO layers as electron transporters for efficient perovskite solar cells.

Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous-titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid-stabilized tin(IV) oxide quantum dots (paa-QD-SnO) on the compact-titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL-perovskite interface. The use of paa-QD-SnO as electron-selective contact enabled PSCs (0.

Coulomb Instabilities of a Three-Dimensional Higher-Order Topological Insulator.

Topological insulators (TIs) are an exciting discovery because of their robustness against disorder and interactions. Recently, second-order TIs have been attracting increasing attention, because they host topologically protected 1D hinge states in 3D or 0D corner states in 2D. A significantly critical issue is whether the second-order TIs also survive interactions, but it is still unexplored.

Field-Tunable One-Sided Higher-Order Topological Hinge States in Dirac Semimetals.

Recently, higher-order topological matter and 3D quantum Hall effects have attracted a great amount of attention. The Fermi-arc mechanism of the 3D quantum Hall effect proposed to exist in Weyl semimetals is characterized by the one-sided hinge states, which do not exist in all the previous quantum Hall systems, and more importantly, pose a realistic example of the higher-order topological matter. The experimental effort so far is in the Dirac semimetal Cd_{3}As_{2}, where, however, time-reversal symmetry leads to hinge states on both sides of the top and bottom surfaces, instead of the aspired one-sided hinge states.