2021 New's Items

Externally driven broadband transmission in strongly disordered materials

Bachelard N
Ropp C
Yang S
Zhang X
2021

In classical and quantum systems, order is of fundamental importance to many branches of science. Still, disorder is prevalent in our natural world. It manifests in various ways, and overcoming its limitations would open up exciting applications. In this work, we numerically show that disorder-induced Anderson localization can be mitigated and transmission systematically restored in random media through a self-organization process relying on energy dissipation. Under the scattering pressure produced by a driving optical field, a colloidal suspension composed of strongly polydisperse...

Self-adaptive acoustic cloak enabled by soft mechanical metamaterials

Xue Y
Zhang X
2021

Acoustic cloaks enable exciting object concealment by manipulating sound waves and have attracted research efforts from different approaches such as transformation acoustics. However, the challenge still lies in the practical implementation of those cloaks that require complex material designs. Here, we show that an underwater acoustic cloak can be automatically achieved by deforming a soft mechanical metamaterial with Poisson’s ratio of -1. The deformation of such an auxetic structure is demonstrated to be able to automatically and passively fulfill the requirement of quasi-...

Organic Hyperbolic Material Assisted Illumination Nanoscopy

Lee YU,
Posner C
Nie Z
Zhao J
Li S
Bopp SE
Wisna GBM
Ha J
Song C
Zhang J
Yang S
Zhang X
Liu Z
2021

Resolution capability of the linear structured illumination microscopy (SIM) plays a key role in its applications in physics, medicine, biology, and life science. Many advanced methodologies have been developed to extend the resolution of structured illumination by using subdiffraction-limited optical excitation patterns. However, obtaining SIM images with a resolution beyond 40 nm at visible frequency remains as an insurmountable obstacle due to the intrinsic limitation of spatial frequency bandwidth of the involved materials and the complexity of the illumination system. Here, a...

Recent Progress on Two-Dimensional Materials

Chang C
Chen W
Chen Y
Zhang X
Zhao LD
Zhao M
Zhao W
Zhao Y
Zhou KG
Zhou X
Zhou Y
Zhu H
Zhang H
Liu Z
2021

Research on two-dimensional (2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some...

Direct electrical modulation of second-order optical susceptibility via phase transitions

Wang Y
Xiao J
Chung TF
Nie Z
Yang S
Zhang X
2021

Electrical modulation of nonlinear optical signals is crucial for emerging applications in communications and photonic circuits. However, current methods of modulating the second-order optical susceptibility involve indirectly and inefficiently changing the third-order susceptibility. Here we show that electrical switching of the crystal structure of monolayer molybdenum ditelluride can be used to directly modulate the second-order susceptibility. This approach leads to modulation of the second-harmonic generation with an on/off ratio of 1,000 and modulation strength of 30,000% per...

Thermodynamics of Composition Dependent Ligand Exchange on the Surfaces of Colloidal Indium Phosphide Quantum Dots

Calvin JJ
O'Brien EA
Sedlak AB
Balan AD
Alivisatos AP
2021

Quantum dot surfaces can have a substantial effect on their physical, chemical, and optoelectronic properties. When the chemistry that occurs at the surface of nanocrystals is studied, critical insights can be gained into the fundamental structural, thermodynamic, and optical properties of quantum dot materials providing a valuable guide for how to best adapt them for desired applications. Colloidal quantum dots are often terminated with organic ligands that consist of a long aliphatic chain and a head group that binds tightly to the nanocrystal surface. While extensive work has been...

Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals

Toso S,
Baranov D
Altamura D
Scattarella F
Dahl J
Wang X
Marras S
Alivisatos AP
Singer A
Giannini C
Manna L
2021

Colloidal superlattices are fascinating materials made of ordered nanocrystals, yet they are rarely called “atomically precise”. That is unsurprising, given how challenging it is to quantify the degree of structural order in these materials. However, once that order crosses a certain threshold, the constructive interference of X-rays diffracted by the nanocrystals dominates the diffraction pattern, offering a wealth of structural information. By treating nanocrystals as scattering sources forming a self-probing interferometer, we developed a multilayer diffraction method that enabled...

Application of Dislocation Theory to Minimize Defects in Artificial Solids Built with Nanocrystal Building Blocks

Ondry JC
Alivisatos AP
2021

Oriented atomic attachment of colloidal inorganic nanocrystals represents a powerful synthetic method for preparing complex inorganic superstructures. Examples include fusion of nanocrystals into dimer and superlattice structures. If the attachment were perfect throughout, then the resulting materials would have single crystal-like alignment of the individual nanocrystals’ atomic lattices. While individual colloidal nanocrystals typically are free of many defects, there are a multitude of pathways that can generate defects upon nanocrystal attachment. These attachment generated defects are...

Single-Particle Studies Reveal a Nanoscale Mechanism for Elastic, Bright, and Repeatable ZnS:Mn Mechanoluminescence in a Low-Pressure Regime

Mukhina MV
Tresback J
Ondry JC
Akey A
Alivisatos AP
Kleckner N
2021

Mechanoluminescent materials, which emit light in response to elastic deformation, are demanded for use as in situ stress sensors. ZnS doped with Mn is known to exhibit one of the lowest reported thresholds for appearance of mechanoluminescence, with repeatable light emission under contact pressure <10 MPa. The physical basis for such behavior remains as yet unclear. Here, reliable microscopic detection of mechanoluminescence of single ZnS:Mn microparticles, in combination with nanoscale structural characterization, provides evidence that the mechanoluminescent...

AutoDetect-mNP: An Unsupervised Machine Learning Algorithm for Automated Analysis of Transmission Electron Microscope Images of Metal Nanoparticles

Wang X
Li J
Ha HD
Dahl JC
Ondry JC
Moreno-Hernandez I
Head-Gordon T
Alivisatos AP
2021

The synthesis quality of artificial inorganic nanocrystals is most often assessed by transmission electron microscopy (TEM) for which high-throughput advances have dramatically increased both the quantity and information richness of metal nanoparticle (mNP) characterization. Existing automated data analysis algorithms of TEM mNP images generally adopt a supervised approach, requiring a significant effort in human preparation of labeled data that reduces objectivity, efficiency, and generalizability. We have developed an unsupervised algorithm AutoDetect-mNP for automated analysis of...