Expanding quasiperiodicity in soft matter: Supramolecular decagonal quasicrystals by binary giant molecule blends

The quasiperiodic structures in metal alloys have been known to depend on the existence of icosahedral order in the melt. Among different phases observed in intermetallics, decagonal quasicrystal (DQC) structures have been identified in many glass-forming alloys yet remain inaccessible in bulk-state condensed soft matters. Via annealing the mixture of two giant molecules, the binary system assemblies into an axial DQC superlattice, which is identified comprehensively with meso-atomic accuracy. Analysis indicates that the DQC superlattice is composed of mesoatoms with an unusually broad volume distribution. The interplays of submesoatomic (molecular) and mesoatomic (supramolecular) local packings are found to play a crucial role in not only the formation of the metastable DQC superlattice but also its transition to dodecagonal quasicrystal and Frank–Kasper σ superlattices.

A physical protocol for observers near the boundary to obtain bulk information in quantum gravity

We consider a set of observers who live near the boundary of global AdS, and are allowed to act only with simple low-energy unitaries and make measurements in a small interval of time. The observers are not allowed to leave the near-boundary region. We describe a physical protocol that nevertheless allows these observers to obtain detailed information about the bulk state. This protocol utilizes the leading gravitational back-reaction of a bulk excitation on the metric, and also relies on the entanglement-structure of the vacuum. For low-energy states, we show how the near-boundary observers can use this protocol to completely identify the bulk state. We explain why the protocol fails completely in theories without gravity, including non-gravitational gauge theories. This provides perturbative evidence for the claim that one of the signatures of holography - the fact that information about the bulk is also available near the boundary - is already visible in the low-energy theory of gravity.

Overcounting of interior excitations: a resolution to the bags of gold paradox in AdS

In this work, we investigate how single-sided and eternal black holes in AdS can host an enormous number of semiclassical excitations in their interior, which is seemingly not reflected in the Bekenstein Hawking entropy. In addition to the paradox in the entropy, we argue that the treatment of such excitations using effective field theory also violates black holes’ expected spectral properties. We propose that these mysteries are resolved because apparently orthogonal semiclassical bulk excitations have small inner products between them; and consequently, a vast number of semiclassical excitations can be constructed using the Hilbert space which describes black hole’s interior. We show that there is no paradox in the dual CFT description and comment upon the initial bulk state, which leads to the paradox. Further, we demonstrate our proposed resolution in the context of small N toy matrix models, where we model the construction of these large number of excitations. We conclude by discussing why this resolution is special to black holes.

Amorphous materials based on perovskite ferroelectrics

The methods of preparation, as well as the structure and most relevant physical properties of amorphous materials based on ferroelectrics with perovskite structure are reviewed. The theoretical basis for the possibility of ferroelectricity in non-crystalline solids is discussed. The structural relaxation in a glassy state and the crystallization processes leading to the formation of a ferroelectric phase are considered. The structure and physical properties of thin-film amorphous ferroelectrics that demonstrate noticeable differences from the properties of the same materials in bulk state are discussed separately

Semiconductor interfaces and junctions

This chapter discusses understanding interfaces, how bulk state reasoning needs to evolve under the constraints of the surface and how these changes relate to interfaces. Interfaces and junctions connect semiconductors to the world and introduce perturbations of their own. Starting with a discussion of the SiO­­­2-Si interface—an amorphous-crystalline interface—with its local evolution, more general conditions—of metals, insulators and semiconductors—with defect states, induced gap states and Fermi pinning are discussed. Next, neutrality level as a defining idea for the establishment of the electronic behavior of metal-semiconductor and semiconductor-semiconductor interfaces is examined. Crystalline continuity leading to heterostructures with conduction band and valence band discontinuities are developed and related to bulk bandstructure. This allows one to analytically describe and show the junction band diagrams of abrupt and graded junctions. Nitride systems often have a polarized junction, that is, have large polarization—spontaneous and often piezoelectric—whose origin is explored.

Eu@PMMA and Sm@PMMA nanofibers prepared by electrospinning: structure, morphology, luminescence and magnetic properties

Eu3+ and Sm3+ coordination polymers and a series of Eu@PMMA and Sm@PMMA nanofibers were prepared. Color tunability was achieved with the luminescence changing from reddish orange in the bulk state to near-white light in the nanofiber stage.