Volume 15 Issue 3, March 2020

When a magnetic field exerts a force on a moving electron it creates direction-dependent phases; hence, it breaks time-reversal symmetry. A nonreciprocal flow of sound is much harder to achieve and requires artificial gauge potentials that give rise to a magnetic field for sound. Mathew, del Pino and Verhagen now implement such a gauge field for vibrations in an on-chip optomechanical system. They use dynamic modulation of strong laser light to induce multi-mode interactions between two nanoscale resonators of different resonance frequencies. The laser light’s radiation pressure force mediates phonon transport between the resonators, but with a phase difference depending on the direction of the phonon transfer. These experiments establish a synthetic gauge field for nanomechanical transport, such that vibrations feel an effective magnetic field. The cover art displays one of the vibrating nanomechanical resonators under strong laser light illumination.

Letter by Verhagen

Image: Ella Maru Studio and Javier del Pino. Cover Design: Bethany Vukomanovic

Editorial

Editorial | 10 March 2020

The risks of nanomaterial risk assessment

The addition of carbon nanotubes to the SIN (‘Substitute It Now’) list has evoked reactions from nanomedicine and nanotoxicology researchers, who ask for a fairer and more recent research-based risk assessment of carbon nanotubes.

Correspondence

Correspondence | 02 March 2020

Grouping all carbon nanotubes into a single substance category is scientifically unjustified
- Bengt Fadeel
- & Kostas Kostarelos
Correspondence | 10 March 2020

Banning carbon nanotubes would be scientifically unjustified and damaging to innovation
- Daniel A. Heller
- , Prakrit V. Jena
- & Masako Yudasaka

News & Views

News & Views | 27 January 2020

Supercool sulfur

On two-dimensional layered materials, elemental sulfur can be controllably generated in a supercooled liquid state with enhanced electrochemical figures of merit compared to solid sulfur.
- Dong Zhou
- & Guoxiu Wang
News & Views | 17 February 2020

Diffusion and transport of extracellular vesicles

Cell-derived extracellular vesicles are important intercellular communicators involved in many biological processes and diseases, including cancer and cardiovascular diseases, but, thus far, how they navigate within complex extracellular matrices has been poorly understood.
- Gregor Fuhrmann

Review Articles

Review Article | 10 March 2020

From nanoscale interface characterization to sustainable energy storage using all-solid-state batteries

This Review summarizes the current nanoscale understanding of the interface chemistries between solid state electrolytes and electrodes for future all solid state batteries.
- Darren H. S. Tan
- , Abhik Banerjee
- & Ying Shirley Meng

Letters

Letter | 20 January 2020

Controlled transformation of skyrmions and antiskyrmions in a non-centrosymmetric magnet

Skyrmions and antiskyrmions are nanometric spin whirls with opposite topological charges. In the Heusler magnet Mn_1.4Pt_0.9Pd_0.1Sn, modulations of the orientation and strength of an in-plane magnetic field induces the transformation from antiskyrmions to non-topological bubbles and skyrmions.
- Licong Peng
- , Rina Takagi
- & Yoshinori Tokura
Letter | 27 January 2020

Layer-resolved magnetic proximity effect in van der Waals heterostructures

Controlling the individual layer magnetization in CrI₃ enables the observation of a layer-resolved magnetic proximity effect in WSe₂/CrI₃ heterostructures.
- Ding Zhong
- , Kyle L. Seyler
- & Xiaodong Xu
Letter | 20 January 2020

Regioselective magnetization in semiconducting nanorods

A double-buffer-layer engineering strategy enables the selective growth of magnetic materials at specific locations on a wide variety of semiconducting nanorods.
- Tao-Tao Zhuang
- , Yi Li
- & Edward H. Sargent
Letter | 03 February 2020

Synthetic gauge fields for phonon transport in a nano-optomechanical system

Gauge fields in condensed matter give rise to nonreciprocal transport and topological non-trivial states. In an on-chip experiment, multi-mode optomechanical interactions generate a magnetic gauge field for nanomechanical motion and yield phonon transport with a nonreciprocal phase.
- John P. Mathew
- , Javier del Pino
- & Ewold Verhagen
Letter | 27 January 2020

Thickness-controlled black phosphorus tunnel field-effect transistor for low-power switches

Tunnel field-effect transistors with spatially varying layer thickness in black phosphorus enable high performance with a record-low subthreshold swing.
- Seungho Kim
- , Gyuho Myeong
- & Sungjae Cho
Collection:
- Monoelemental 2D materials
Letter | 20 January 2020

Single-molecule tautomerization tracking through space- and time-resolved fluorescence spectroscopy

Tautomerization, the interconversion between two constitutional isomers of a molecule, plays a major role in chemistry. The combination of hyper-resolved fluorescence microscopy with time-correlated measurements and spectral selection enables the identification and in-depth characterization of a tautomerization reaction within a single molecular switch.
- Benjamin Doppagne
- , Tomáš Neuman
- & Guillaume Schull
Collection:
- Sensing at the limit
Letter | 06 January 2020

Tuning inelastic light scattering via symmetry control in the two-dimensional magnet CrI₃

Symmetry control in atomically thin chromium triiodide enables the observation of tunable magneto-optical Raman effects in the 2D limit.
- Bevin Huang
- , John Cenker
- & Xiaodong Xu
Letter | 17 February 2020

Matrix mechanics and water permeation regulate extracellular vesicle transport

Stress relaxation properties of the matrix as well as water transport through aquaporin-1 enable extracellular vesicles to deform and travel through the dense mesh of the extracellular matrix between cells.
- Stephen Lenzini
- , Raymond Bargi
- & Jae-Won Shin

Articles

Article | 27 January 2020

Real-time mass spectrometric characterization of the solid–electrolyte interphase of a lithium-ion battery

An operando mass spectrometry technique, along with molecular dynamics simulations, unveils the evolution of the solid–electrolyte interphase chemistry and structure in lithium-ion batteries during the first cycle.
- Yufan Zhou
- , Mao Su
- & Zihua Zhu
Article | 27 January 2020

Electrochemical generation of liquid and solid sulfur on two-dimensional layered materials with distinct areal capacities

A supercooled liquid phase of elemental sulfur can be grown electrochemically on two-dimensional materials. This phase has a markedly higher areal capacity than solid sulfur, with possible implications for future lithium–sulfur batteries.
- Ankun Yang
- , Guangmin Zhou
- & Yi Cui