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Author(s): H. H. Fang, B. Han, C. Robert, M. A. Semina, D. Lagarde, E. Courtade, T. Taniguchi, K. Watanabe, T. Amand, B. Urbaszek, M. M. Glazov, and X. Marie

Optical properties of atomically thin transition metal dichalcogenides are controlled by robust excitons characterized by a very large oscillator strengths. Encapsulation of monolayers such as MoSe2 in hexagonal boron nitride (hBN) yields narrow optical transitions approaching the homogenous exciton...

[Phys. Rev. Lett. 123, 067401] Published Mon Aug 05, 2019

Author(s): J. Bekaert, M. Petrov, A. Aperis, P. M. Oppeneer, and M. V. Milošević

Hydrogen-based compounds under ultrahigh pressure, such as the polyhydrides H3S and LaH10, superconduct through the conventional electron-phonon coupling mechanism to attain the record critical temperatures known to date. Here we exploit the intrinsic advantages of hydrogen to strongly enhance phono...

[Phys. Rev. Lett. 123, 077001] Published Tue Aug 13, 2019

Author(s): Bruno Schuler, Diana Y. Qiu, Sivan Refaely-Abramson, Christoph Kastl, Christopher T. Chen, Sara Barja, Roland J. Koch, D. Frank Ogletree, Shaul Aloni, Adam M. Schwartzberg, Jeffrey B. Neaton, Steven G. Louie, and Alexander Weber-Bargioni

Atomic force and scanning tunneling microscopy correlate the structure and electronic properties of single-atom defects in the transitional metal dichalcogenide WS2.

[Phys. Rev. Lett. 123, 076801] Published Tue Aug 13, 2019

Author(s): J. J. Esteve-Paredes, Sahar Pakdel, and J. J. Palacios

We predict that long-lived excitons with very large binding energies can also exist in a single or few layers of monochalcogenides such as GaSe. Our theoretical study shows that excitons confined by a radial local strain field are unable to recombine despite electrons and holes coexisting in space. ...

[Phys. Rev. Lett. 123, 077402] Published Wed Aug 14, 2019

Here, recent advances in exfoliation and modification of layered two‐dimensional (2D) materials in various supercritical fluids (SCFs) are highlighted. The motivating factors for enhancing exfoliation efficiency and product quality in SCFs, mechanisms for exfoliation and dispersion in SCFs, as well as general metrics applied to assess quality and processability of exfoliated 2D materials are critically discussed.

Abstract

Since the first intercalation of layered silicates by using supercritical CO₂ as a processing medium, considerable efforts have been dedicated to intercalating and exfoliating layered two‐dimensional (2D) materials in various supercritical fluids (SCFs) to yield single‐ and few‐layer nanosheets. Here, recent work in this area is highlighted. Motivating factors for enhancing exfoliation efficiency and product quality in SCFs, mechanisms for exfoliation and dispersion in SCFs, as well as general metrics applied to assess quality and processability of exfoliated 2D materials are critically discussed. Further, advances in formation and application of 2D material–based composites with assistance from SCFs are presented. These discussions address chemical transformations accompanying SCF processing such as doping, covalent surface modification, and heterostructure formation. Promising features, challenges, and routes to expanding SCF processing techniques are described.

A large‐area, highly polarization‐sensitive and broadband photodetector based on multilayered PdSe₂/perovskite device is demonstrated. From optoelectronic characterization, the device achieves an impressive specific detectivity of ≈10¹³ Jones, a polarization sensitivity as high as 6.04, and a fast response speed of 3.5/4 µs. Further study reveals that the present device is potentially important for image sensor applications.

Abstract

Group‐10 transition metal dichalcogenides (TMDs) with distinct optical and tunable electrical properties have exhibited great potential for various optoelectronic applications. Herein, a self‐powered photodetector is developed with broadband response ranging from deep ultraviolet to near‐infrared by combining FA_{1− x} Cs _x PbI₃ perovskite with PdSe₂ layer, a newly discovered TMDs material. Optoelectronic characterization reveals that the as‐assembled PdSe₂/perovskite Schottky junction is sensitive to light illumination ranging from 200 to 1550 nm, with the highest sensitivity centered at ≈800 nm. The device also shows a large on/off ratio of ≈10⁴, a high responsivity (R) of 313 mA W⁻¹, a decent specific detectivity (D*) of ≈10¹³ Jones, and a rapid response speed of 3.5/4 µs. These figures of merit are comparable with or much better than most of the previously reported perovskite detectors. In addition, the PdSe₂/perovskite device exhibits obvious sensitivity to polarized light, with a polarization sensitivity of 6.04. Finally, the PdSe₂/perovskite detector can readily record five “P,” “O,” “L,” “Y,” and “U” images sequentially produced by 808 nm. These results suggest that the present PdSe₂/perovskite Schottky junction photodetectors may be useful for assembly of optoelectronic system applications in near future.

2D black mica (BM)‐based nanosheets (NSs) are fabricated through an exfoliation approach that combines grinding, calcination, n‐butyllithium exchange and intercalation, and liquid exfoliating processes. The nanoplatform based on PEGylated BM NSs exhibits multiple features, such as tumor microenvironment modulation, efficient reactive oxygen species production and photothermal conversion, high tumor site accumulation, good biocompatibility, and multimodal imaging‐guided breast cancer treatment.

Abstract

Biotite, also called black mica (BM), is a group of sheet silicate minerals with great potential in various fields. However, synthesis of high‐quality BM nanosheets (NSs) remains a huge challenge. Here, an exfoliation approach is provided that combines calcination, n‐butyllithium exchange and intercalation, and liquid exfoliating processes for the high‐yield synthesis of ultrathin BM NSs. Due to the presence of MgO, Fe₂O₃, and FeO in these NSs, PEGylated BM can be engineered as an intelligent theranostic platform with the following unique features: i) Fe³⁺ can damage the tumor microenvironment (TME) through glutathione consumption and O₂ production; ii) Generated O₂ can be further catalyzed by MgO with oxygen vacancy to generate ·O₂ ⁻; iii) The Fe²⁺‐catalyzed Fenton reaction can produce ·OH by disproportionation reactions of H₂O₂ in the TME; iv) Reactions in (i) and (iii) circularly regenerate Fe²⁺ and Fe³⁺ for continuous consumption of glutathione and H₂O₂ and constant production of ·OH and O₂; v) The NSs can be triggered by a 650 nm laser to generate ·O₂ ⁻ from O₂ as well as by an 808 nm laser to generate local hyperthermia; and vi) The fluorescent, photoacoustic, and photothermal imaging capabilities of the engineered NSs allow for multimodal imaging‐guided breast cancer treatment.

When two sheets of graphene are stacked at a small twist angle, the resulting flat superlattice minibands are expected to strongly enhance electron-electron interactions. Here, we present evidence that near three-quarters () filling of the conduction miniband, these enhanced interactions drive the twisted bilayer graphene into a ferromagnetic state. In a narrow density range around an apparent insulating state at , we observe emergent ferromagnetic hysteresis, with a giant anomalous Hall (AH) effect as large as 10.4 kilohms and indications of chiral edge states. Notably, the magnetization of the sample can be reversed by applying a small direct current. Although the AH resistance is not quantized, and dissipation is present, our measurements suggest that the system may be an incipient Chern insulator.

Nature Reviews Materials, Published online: 19 August 2019; doi:10.1038/s41578-019-0136-x

2D materials exhibit diverse properties and can be integrated in heterostructures: this makes them ideal platforms for quantum information science. This Review surveys recent progress and identifies future opportunities for 2D materials as quantum-dot qubits, single-photon emitters, superconducting qubits and topological quantum computing elements.