Correlation between boson peak and thermal expansion manifested by physical aging and high pressure

We investigate the effects of high pressure and physical aging on the boson peak and thermal expansion of a typical metallic glass. Specifically, the thermal expansion coefficient and boson peak intensity monotonically decrease during physical aging.With the increase of high pressure, the boson peak intensity and the thermal expansion coefficient coincidently experience an incipient decrease and then a subsequent increase. The boson peak intensity shows an approximately linear relationship with the thermal expansion coefficient. The thermal expansion can be affected by structural relaxation or rejuvenation, which can reflect the flow units variation and atomic packing of a metallic glass. Our results indicate a direct link between structural relaxation or rejuvenation and fast boson peak dynamics, providing insights into the boson peak behavior and structural heterogeneity of metallic glasses.

Experimental research on thermal transport properties of crystallized palladium-based alloys

Palladium-based alloy is a kind of material with a high glass forming ability and can be easily formed into an amorphous state. After an annealing process, it can also be maintained at a crystallized state. To study the thermal and electrical transport properties of crystallized palladium-based alloys, the steady-state T-type method, standard four-probe method, and AC heating-DC detecting T-type method were used to measure the thermal conductivity, electrical conductivity, and Seebeck coeffi- cient of crystallized Pd4oNiloCu3oP2o and Pd43Nilo- Cu27P2o alloys respectively. The results show that compared to amorphous samples, the thermal conductivity and electrical conductivity of crystallized palladium-based alloys are significantly higher, while the Seebeck coeffi- cient is lower. The ratio of crystallized and amorphous thermal conductivity is higher for Pd43Ni10Cu27P2o alloy fiber which has a higher glass forming ability, while the ratio of electronic thermal conductivity almost remains constant for both alloy fibers. The results also show that the slope of electrical resistivity to temperature is a function of elemental composition for crystallized quaternary palla- dium-based alloy fibers. The sensitivity of thermal conductivity and electrical conductivity to the composition is high, while the correlation between Seebeck coefficient and composition is relatively weak.

Two-dimensional Stiefel-Whitney insulators in liganded Xenes

Two-dimensional(2D)Stiefel-Whitney insulator(SWI),which is characterized by the second Stiefel-Whitney class,is a class of topological phases with zero Berry curvature.As an intriguing topological state,it has been well studied in theory but seldom realized in realistic materials.Here we propose that a large class of liganded Xenes,i.e.,hydrogenated and halogenated 2D group-IV honeycomb lattices,are 2D SWIs.The nontrivial topology of liganded Xenes is identified by the bulk topological invariant and the existence of protected corner states.Moreover,the large and tunable bandgap(up to 3.5 eV)of liganded Xenes will facilitate the experimental characterization of the 2D SWI phase.Our findings not only provide abundant realistic material candidates that are experimentally feasible but also draw more fundamental research interest towards the topological physics associated with Stiefel-Whitney class in the absence of Berry curvature.