Structural and Dynamical Properties of Metallic Glassy Films

In this chapter, a series of molecular dynamics simulations have been carried out to explore structural and dynamical features of monatomic liquid metallic films during rapid cooling. Results show a semi‐ordered inhomogeneous morphology containing crystal‐like and disordered regions. The icosahedron contributes to nucleation through the synergy with other short‐range ordered structures and participates in crystal growth via assimilation, but the pinning effect should be overcome. The second‐peak splitting in pair correlation functions is found as the result of a statistical average of crystal‐like and disordered structural regions, not just the amorphous structure. The splitting can be viewed as a prototype of crystal‐like peaks exhibiting distorted and vestigial features. Besides, we use the parameter P(a, τ, ν) for predicting both local structural order and motion propensity. The fraction of crystalline clusters follows a negative power‐law scaling with the cooling rate increasing, which is the inverse of P(a, τ, ν)

Chiral Phonons in Chiral Materials

The concept of chirality makes ubiquitous appearance in nature. Particularly, both a structure and its collective excitations may acquire well defined chiralities. In this work, we reveal an intrinsic connection between the chiralities of a crystal structure and its phonon excitations. We show that the phonon chirality and its propagation direction are strongly coupled with the lattice chirality, which will be reversed when a chiral lattice is switched to its enantiomorph. In addition, distinct from achiral lattices, propagating chiral phonons exist for chiral crystals also on the principal axis through the $\Gamma$ point, which strengthens its relevance to various physical processes. We demonstrate our theory with a 1D helix-chain model and with a concrete and important 3D material, the $\alpha$-quartz. We predict a chirality diode effect in these systems, namely, at certain frequency window, a chiral signal can only pass the system in one way but not the other, specified by the system chirality. Experimental setups to test our theory are proposed. Our work discovers fundamental physics of chirality coupling between different levels of a system, and the predicted effects will provide a new way to control thermal transport and design information devices.Comment: 5 pages, 5 figure

Resonant tunneling diode oscillators for optical communications

The ability to use resonant tunneling diodes (RTDs) as both transmitters and receivers is an emerging topic, especially with regards to wireless communications. Successful data transmission has been achieved using electronic RTDs with carrier frequencies exceeding 0.3 THz. Specific optical-based RTDs, which act as photodetectors, have been developed by adjusting the device structure to include a light absorption layer and small optical windows on top of the device to allow direct optical access. This also allows the optical signal to directly modulate the RTD oscillation. Both types of RTD oscillators will allow for seamless integration of high frequency radio and optical fiber networks.European Union's Horizon research and innovation programme [645369