jinzhitong

Ferroelectricity is generated in twisted hBN flakes, which are used as a ferroelectric tunneling junction. Spatially resolved investigation by a conductive atomic force microscope tip reveals the unconventional ferroelectricity in this system, including lattice-slide-induced domain change, an unusual relationship between the tunneling resistance and polarization, and highly spatially dependent ferroelectric hysteresis.

Abstract

Robust room-temperature interfacial ferroelectricity has been formed in the 2D limit by simply twisting two atomic layers of non-ferroelectric hexagonal boron nitride (hBN). A thorough understanding of this newly discovered ferroelectric system is required. Here, twisted hBN is used as a tunneling junction and it is studied at the nanometer scale using conductive atomic force microscopy. Three properties unique to this system are discovered. First, the polarization dependence of the tunneling resistance contrasts with the conventional theory. Second, the ferroelectric domains can be controlled using mechanical stress, highlighting the original meaning of the emergent “slidetronics”. Third, ferroelectric hysteresis is highly spatially dependent. The hysteresis is symmetric at the domain walls. A few nanometers away, the hysteresis shifts completely to the positive or negative side, depending on the original polarization. These findings reveal the unconventional ferroelectricity in this 2D system.

Nature Communications, Published online: 27 October 2022; doi:10.1038/s41467-022-33978-3

The ferroelectric material α-GeTe(111) is an excellent playground for spin-to charge conversion due to its strong Rashba coupling. Here, the authors reveal an ultrafast modulation of its Rashba coupling on the femtosecond timescale.

Nature Electronics, Published online: 27 October 2022; doi:10.1038/s41928-022-00849-0

Gate-tunable heterojunction diodes—or triodes—that are based on van der Waals heterostructures formed from two-dimensional indium selenide and three-dimensional silicon can exhibit subthreshold slopes of 6.4 mV decade–1 and on-state current densities of 0.3 µA µm–1 at a drain bias of –1 V.

Nature Nanotechnology, Published online: 24 October 2022; doi:10.1038/s41565-022-01222-0

Twisting bilayer graphene to specific angles can yield correlated phases. A superconducting quantum interference device made from this magic-angle twisted bilayer graphene makes it possible to control the phase drop across a Josephson junction in this material.

Nature Nanotechnology, Published online: 24 October 2022; doi:10.1038/s41565-022-01235-9

Parametric amplifiers enable the low noise readout of systems with intrinsically low energy scales. Now, a parametric amplifier leveraging a graphene Josephson junction exhibits a gate-tunable working frequency and a gain exceeding 20 dB with added noise close to the standard quantum limit.

Nature Nanotechnology, Published online: 27 October 2022; doi:10.1038/s41565-022-01230-0

Isothermal dissolution–diffusion–precipitation of carbon drives continuous epitaxial growth of single-crystal multilayer graphene.

Nature Nanotechnology, Published online: 29 October 2022; doi:10.1038/s41565-022-01223-z

Low-noise amplification of feeble microwave signals is essential for superconducting quantum circuitry. Now, a gate-tunable Josephson parametric amplifier made from graphene shows 24 dB amplification paired with 10 MHz bandwidth and –130 dBm saturation power.

Nature Materials, Published online: 25 October 2022; doi:10.1038/s41563-022-01382-3

Two-dimensional electrons on the surface of an electride are found to exhibit a phase transition from a normal Fermi liquid to an interesting quantum liquid, which is probably a quantum version of an electronic crystal beyond the melting point.

Nature Materials, Published online: 25 October 2022; doi:10.1038/s41563-022-01378-z

Twisted bilayer graphene is epitaxially grown between two adjacent Cu(111) surfaces, with the twist angle controlled by the rotation of the Cu foils as designed.

Nature Materials, Published online: 27 October 2022; doi:10.1038/s41563-022-01386-z

Using molecular-beam epitaxy, we synthesize heterostructures of topological insulator Bi2Se3 and the Ising superconductor monolayer NbSe2. By changing the Bi2Se3 thickness, they demonstrate a crossover from Ising- to Rashba-type superconducting pairing.

Nature Materials, Published online: 25 October 2022; doi:10.1038/s41563-022-01383-2

This Review discusses the progress in and potential pathways for incorporating two-dimensional materials into silicon platforms, from integrated devices to monolithic circuits.

Nature, Published online: 26 October 2022; doi:10.1038/s41586-022-05261-4

An unusual new material, NiTTFtt, is reported that is structurally amorphous, precluding a classical band structure, but detailed characterization reveals high conductivity and a metallic character.

Magnetic skyrmions and large topological Hall effect are demonstrated in chromium telluride. The Curie temperature and magnetic anisotropy in Cr_{1+ x} Te₂ can be controlled by the self-intercalate concentration x. In Cr_1.53Te₂, which has a Curie temperature of 295 K and a relatively weak perpendicular magnetic anisotropy, room-temperature skyrmions and topological Hall resistivity as large as ≈106 nΩ cm are observed.

Abstract

Room-temperature magnetic skyrmion materials exhibiting robust topological Hall effect (THE) are crucial for novel nano-spintronic devices. However, such skyrmion-hosting materials are rare in nature. In this study, a self-intercalated transition metal dichalcogenide Cr_{1+ x} Te₂ with a layered crystal structure that hosts room-temperature skyrmions and exhibits large THE is reported. By tuning the self-intercalate concentration, a monotonic control of Curie temperature from 169 to 333 K and a magnetic anisotropy transition from out-of-plane to the in-plane configuration are achieved. Based on the intercalation engineering, room-temperature skyrmions are successfully created in Cr_1.53Te₂ with a Curie temperature of 295 K and a relatively weak perpendicular magnetic anisotropy. Remarkably, a skyrmion-induced topological Hall resistivity as large as ≈106 nΩ cm is observed at 290 K. Moreover, a sign reversal of THE is also found at low temperatures, which can be ascribed to other topological spin textures having an opposite topological charge to that of the skyrmions. Therefore, chromium telluride can be a new paradigm of the skyrmion material family with promising prospects for future device applications.

Nature Photonics, Published online: 17 October 2022; doi:10.1038/s41566-022-01080-1

Researchers show that resonant coupling of light pulses with excitonic transitions affects the optimal time difference between pulses for sum-frequency generation and four-wave mixing in monolayer WSe2.

Nature Nanotechnology, Published online: 20 October 2022; doi:10.1038/s41565-022-01221-1

A one-step simultaneous van der Waals integration of high-k dielectrics and contacts enables the realization of top-gated transistors with atomically clean and electronically sharp interfaces.

Nature Electronics, Published online: 13 October 2022; doi:10.1038/s41928-022-00847-2

A reservoir computing system for multimode and multiscale signal processing can be created using optoelectronic synapses that are based on α-In2Se3 and exploit the tightly coupled ferroelectric and optoelectronic properties of the material.

Nature Physics, Published online: 13 October 2022; doi:10.1038/s41567-022-01778-7

The superconducting critical temperature of monolayer materials is often lower than their bulk counterparts. Now, intercalation is shown to induce two-dimensional superconducting properties while maintaining the bulk critical temperature.