Containerless processing or ‘levitation’ is a valuable tool for the synthesis and characterization of materials, particularly at extreme temperatures and under non-equilibrium conditions. The method enables formation of novel glasses, amorphous phases, and metastable crystalline forms that are not easily accessed when nucleation and growth can readily occur at a container interface. Removing the container enables the use of a wide variety of process atmospheres to modify a materials structure and properties. In the past decade levitation methods, including acoustic, aerodynamic, electromagnetic, and electrostatic, have become well established sample environments at X-ray synchrotron and neutron sources. This article briefly reviews the methods and then focuses on the application of aerodynamic levitation to synthesize and study new materials. This is presented in conjunction with non-contact probes used to investigate the atomic structure and to measure the properties of materials at extreme temperatures. The use of aerodynamic levitation in research using small and wide-angle X-ray diffraction, XANES, and neutron scattering are discussed in the context of technique development. The use of the containerless methods to investigate thermophysical properties is also considered. We argue that structural motifs and in the liquid state can potentially lead to the fabrication of materials, whose properties would differ substantially from their well known crystalline forms.

The s-electrons of alkali metals loaded into regular nanospaces (nanocages) of zeolite crystals display novel electronic properties, such as a ferrimagnetism, a ferromagnetism, an antiferromagnetism, an insulator-to-metal transition, etc., depending on the kind of alkali metals, their loading density, and the structure type of zeolite frameworks. These properties are entirely different from those in bulk alkali metals of free-electrons. Alkali-metal clusters are stabilized in cages of zeolites, and new quantum states of s-electrons, such as 1s, 1p, and 1d states in the spherical quantum-well model, are formed. An electron correlation, a polaron effect, and an orbital degeneracy in the quantum states of s-electrons play critical roles in taking on the novel electronic properties. Electronic properties can be overviewed systematically by a coarse-grained model of localized s-electron states in cages based on the tight-binding approximation, followed by the t-U-S-n diagram of the correlated polaron system given by the so-called Holstein–Hubbard Hamiltonian: an electron transfer energy through windows of cages (t), a Coulomb repulsion energy between two s-electrons in the same cage (U), a short-range electron-phonon interaction energy due to the cation displacements (S), and an average number of s-electrons per cage (n). Beyond the jellium background model of alkali-metal clusters, a huge spin-orbit interaction has been observed in the 1p degenerate orbitals of clusters, similarly to the Rashba mechanism.

The colloidal route is an important methodology in ceramic processing. A key step of the colloidal route is the aggregation of colloids in suspension. This often involves colloids of different types, in a process which is known as heteroaggregation. Here we review the recent developments in ceramic heteroaggregation, focusing on the physical mechanisms that cause it and on the structural properties of the resulting aggregates. Structural properties are analysed both on the local scale, at the level of nearest-neighbour contacts between colloids and on the long-range scale, at which percolating aggregates form, leading to gelification. Both experimental and simulation results are reviewed. The effects of the structure of the aggregates on the subsequent steps of ceramic processing are discussed.

We review the optical physics of Josephson plasmons in cuprate superconductors. These coherent charge modes arise from tunneling of the superfluid between superconducting planes and exhibit strong nonlinearities and quantum coherent dynamics at THz frequencies. We summarize early transport and microwave experiments in Bi2Sr2CaCu2O8+δ (BSCCO) and discuss more recent work performed in La2−xSrxCuO4 (LSCO) and La2−xBaxCuO4 (LBCO) using nonlinear THz techniques. We cover THz-driven oscillations between superconducting and resistive states, optical excitation of solitonic breathers, and the parametric amplification of Josephson plasma waves. The last part of the review discusses some new research directions, including cooling of superconducting phase fluctuations with lasers and optical cavity control techniques.

Proteins are the main executors of complicated biological functions in nature. All the function-related structures and dynamics of proteins are encoded through the sequences with a 20-letter amino acid alphabet. Though the amino acid alphabets and the sequences are much more complex than that of the nucleic acids, the ubiquitous structural and functional homologs suggest there is much redundancy in the sequences and the alphabets. The discovery of the hidden simplicity of the amino acid alphabet could greatly help to disclose the regularities of protein systems and may stimulate some novel designs of protein, and has become one area in biological physics with continuous attentions. Physically, this kind of simplicity is a reflection and requirement of the folding landscape of proteins. In this review, we would like to describe the simplification problem of amino acid alphabet from physics aspect. The resultant extensions in bioinformatics and the relevant physical implications would also be discussed.

Two-dimensional (2D) boron, as an analog of graphene, can serve as a building block for fullerenes, nanotubes, and nanoribbons. Understanding its structure and stability is a prerequisite for studies of all those boron nanostructures. Based on an ab initio evolutionary structure search, novel 2D boron structures with nonzero thickness were predicted. In particular, the formation of 2D Dirac boron was reviewed.

We review measurements of the dielectric properties of metals, which have resurfaced as a timely topic given the ongoing interest in plasmonics across a broad range of the electromagnetic spectrum. It is generally accepted that the Drude model fully describes the optical response of metals. This is certainly true at optical frequencies. This also appears to be the case when THz time-domain spectroscopy is used to measure the properties of thin films. However, for a variety of plasmonics-based implementations in the terahertz (THz) spectral range, there appear to be significant discrepancies. We discuss these observations, as well as a new family of measurement techniques based on the excitation and detection of surface plasmon-polaritons. Finally, we conclude with a brief discussion regarding the implications of these new measurements for the field of THz plasmonics.

It is now possible to establish the chemical identity of a substance at the ultimate detection limit of a single molecule, i.e. the sensitivity required to probe 1.66 yoctomoles (1/NA), using surface-enhanced Raman scattering (SERS). It is also possible to image within an individual molecule, all while retaining chemical selectivity, using tip-enhanced Raman scattering (TERS). The potential applications of ultrasensitive SERS and TERS in chemical and biological detection and imaging are evident, and have attracted significant attention over the past decade. Rather than focusing on conventional single/few-molecule SERS and TERS experiments, where the objective is ultrasensitive spectroscopy and nanoscale chemical imaging, herein we consider greatly informative, yet significantly underrated, signatures of single molecules. Namely, we review recent efforts ultimately aimed at probing different aspects of a molecule’s local environment through a detailed analysis of its SERS and TERS spectra and images. Particular attention is devoted to local electric field imaging using TERS; we describe how the vector components and absolute magnitude of the local electric field may be inferred from molecular Raman signatures. We also propose experiments that can potentially be used to cross-check the insights gained from the described SERS and TERS measurements. The ultimate goal of this review is to demonstrate that there is much more to single-molecule Raman scattering than mere ultrasensitive chemical analysis.