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Td-WTe 2 (non-centrosymmetric and orthorhombic), a type-II Weyl semimetal, is expected to have higher-order topological phases with topologically protected, helical one-dimensional hinge states when its Weyl points are annihilated. However, the detection of these hinge states is difficult due to the semimetallic behaviour of the bulk. In this study, we have spatially resolved the hinge states by analysing the magnetic field interference of the supercurrent in Nb–WTe 2 –Nb proximity Josephson junctions. The Josephson current along the a axis of the WTe 2 crystal, but not along the b axis, showed a sharp enhancement at the edges of the junction, and the amount of enhanced Josephson current was comparable to the upper limits of a single one-dimensional helical channel. Our experimental observations suggest a higher-order topological phase in WTe 2 and its corresponding anisotropic topological hinge states, in agreement with theoretical calculations. Our work paves the way for the study of hinge states in topological transition-metal dichalcogenides and analogous phases. Transport measurements and calculations show that WTe 2 may be a higher-order topological insulator with topological hinge states.

Crystalline solids can become band insulators due to fully filled bands, or Mott insulators due to strong electronic correlations. While Mott insulators can theoretically occur in systems with an even number of electrons per unit cell, distinguishing them from band insulators experimentally has remained a longstanding challenge. In this work, we present a unique momentum-resolved signature of a dimerized Mott-insulating phase in the experimental spectral function of Nb 3 Br 8 : the top of the highest occupied band along the out-of-plane direction k z has a momentum-space separation Δk z = 2 π / d , whereas that of a band insulator is less than π / d , where d is the average interlayer spacing. Identifying Nb 3 Br 8 as a Mott insulator is crucial to understand its role in the field-free Josephson diode effect. Moreover, our method could be extended to other van der Waals systems where tuning interlayer coupling and Coulomb interactions can drive a band- to Mott-insulating transition. Distinguishing band and Mott insulators experimentally represents a longstanding challenge. Here, the authors demonstrate a momentum-resolved signature of a dimerized Mott-insulator in the out-of-plane spectral function of Nb 3 Br 8 .

An amendment to this paper has been published and can be accessed via a link at the top of the paper.An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Simultaneous breaking of inversion and time-reversal symmetries in a conductor yields a non-reciprocal electronic transport 1 – 3 , known as the diode or rectification effect, that is, low (ideally zero) conductance in one direction and high (ideally infinite) conductance in the other. So far, most of the diode effects observed in non-centrosymmetric polar/superconducting conductors 4 – 7 and Josephson junctions 8 – 10 require external magnetic fields to break the time-reversal symmetry. Here we report zero-field polarity-switchable Josephson supercurrent diodes, in which a proximity-magnetized Pt layer by ferrimagnetic insulating Y 3 Fe 5 O 12 serves as the Rashba(-type) Josephson barrier. The zero-field diode efficiency of our proximity-engineered device reaches up to ±35% at 2 K, with a clear square-root dependence on temperature. Measuring in-plane field-strength/angle dependences and comparing with Cu-inserted control junctions, we demonstrate that exchange spin-splitting 11 – 13 and Rashba(-type) spin-orbit coupling 13 – 15 at the Pt/Y 3 Fe 5 O 12 interface are key for the zero-field giant rectification efficiency. Our achievement advances the development of field-free absolute Josephson diodes. A rectified Josephson supercurrent is realized in lateral junctions using a proximitized ferromagnetic Pt barrier, with important implications for practical magnetic field free-superconducting spintronics.

Chirality is a ubiquitous and fundamental asymmetry in nature 1 , 2 . Recently, the interaction of chiral objects with spin currents has attracted enormous attention from both scientific and technological perspectives 3 , 4 – 5 . Of particular interest is the current-driven motion of chiral topological excitations such as chiral magnetic domain walls in chiral three-dimensional magnetic structures that could allow for high-density memory-storage devices. Here we use state-of-the-art multiphoton lithography 6 , 7 to create three-dimensional chiral magnetic ribbons and perform current-induced motion of chiral domain walls. The ribbons are designed to have a clockwise or anticlockwise chiral twist with a variable magnitude. We find that domain walls can either pass through the ribbon or are impeded, depending on their chirality and configuration and the geometrical chiral twist of the ribbon. The interplay between the magnetic exchange energy and the geometrical twist generates a torsional field that favours chiral Bloch-type walls rather than the Néel-type wall favoured by the intrinsic magnetic properties of the magnetic ribbon itself. Furthermore, the interplay of spin chirality and chiral twist results in a non-reciprocal domain wall motion, namely, a domain wall filter or diode 8 , 9 – 10 . Our findings show how the interplay between geometrical and spin chiralities can lead to new functionalities that could allow for innovative chiral spintronics. The interplay between geometrical and spin chiralities in three-dimensional twisted magnetic ribbons can lead to new functionalities that could allow for innovative chiral spintronics.

Over the past two decades, since the emergence of the triple bottom line philosophy, the relationship between environmental sustainability and corporate performance has received a lot of attention, but has generated mixed or often even contradictory results. A few recent studies have inferred that innovations are the missing link that connects the environmental sustainability of a firm to other performance metrics; however, the evidence of such a proposition has been restricted to being conceptual or anecdotal. Relying on a knowledge governance approach, this study presents exploratory empirical evidence indicating that the impacts of a firm’s sustainability initiatives on its innovation performance originate from the governance mechanism it uses for sustainability, not sustainability outcomes per se. We tested this research proposition by using a subsample of Global Manufacturing Research Group’s global survey data. Our results support the positive impacts of two widely-used environmental sustainability governance mechanisms (i.e., internal monitoring and supplier collaboration) on product innovation capability. The findings further provide more useful and effective options for manufacturing firms and managers, to establish environmental sustainability governance mechanisms that can be converted into product innovation capability.

Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains 1 , 2 , whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling 3 , 4 – 5 . Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.59 Å and periodic rhombohedral lattices formed by interwoven polyaniline chains. Electron spin resonance spectroscopy reveals significant electron delocalization in the 2DPANI lattices. First-principles calculations indicate the in-plane 2D conjugation and strong interlayer electronic coupling in 2DPANI facilitated by the Cl-bridged layer stacking. To assess the local optical conductivity, we used terahertz and infrared nanospectroscopy to unravel a Drude-type conductivity with an infrared plasma frequency and an extrapolated local d.c. conductivity of around 200 S cm −1 . Conductive scanning probe microscopy showed an unusually high out-of-plane conductivity of roughly 15 S cm −1 . Transport measurements through vertical and lateral micro-devices revealed comparable high out-of-plane (roughly 7 S cm −1 ) and in-plane conductivity (roughly 16 S cm −1 ). The vertical micro-devices further showed increasing conductivity with decreasing temperature, demonstrating unique out-of-plane metallic transport behaviour. By using this multilayer-stacked 2D conducting polymer design, we predict the achievement of strong electronic coupling beyond in-plane interactions, potentially reaching three-dimensional metallic conductivity 6 , 7 . A multilayer-stacked two-dimensional polyaniline crystal shows high electrical conductivity and unique out-of-plane metallic transport behaviour, indicating potential for strong electronic coupling beyond in-plane interactions and three-dimensional metallic conductivity.

Of great promise are synthetic antiferromagnet-based racetrack devices in which chiral composite domain walls can be efficiently moved by current. However, overcoming the trade-off between energy efficiency and thermal stability remains a major challenge. Here we show that chiral domain walls in a synthetic antiferromagnet–ferromagnet lateral junction are highly stable against large magnetic fields, while the domain walls can be efficiently moved across the junction by current. Our approach takes advantage of field-induced global energy barriers in the unique energy landscape of the junction that are added to the local energy barrier. We demonstrate that thermal fluctuations are equivalent to the magnetic field effect, thereby, surprisingly, increasing the energy barrier and further stabilizing the domain wall in the junction at higher temperatures, which is in sharp contrast to ferromagnets or synthetic antiferromagnets. We find that the threshold current density can be further decreased by tilting the junction without affecting the high domain wall stability. Furthermore, we demonstrate that chiral domain walls can be robustly confined within a ferromagnet region sandwiched on both sides by synthetic antiferromagnets and yet can be readily injected into the synthetic antiferromagnet regions by current. Our findings break the aforementioned trade-off, thereby allowing for versatile domain-wall-based memory, and logic, and beyond. Introducing local, nanoscopic ferromagnetic regions in a synthetic antiferromagnet racetrack can help to mitigate the trade-off between energy efficiency and thermal stability in magnetic domain-wall-based devices.