Interest in low-dimensional magnetic systems surged with the discovery of magnetism in some quasi-2D materials. While ferro- and ferrimagnetic compounds gained attention, antiferromagnetic semiconductors like Metal-transition phospho-trichalcogenides (MPX3) remained less studied. MPX3s are quasi-2D van der Waals semiconductors with diverse antiferromagnetic spin configurations. In this talk, I will describe the properties of acoustic phonons in such materials probed by Brillouin-Mandelstam inelastic light scattering. Acoustic phonons carry heat and contribute to electron–phonon, and magnon–phonon scattering processes. We observed significant variations in acoustic phonon velocities among materials with similar structures. Correlations with available thermal transport data underscore the importance of our findings for understanding layered vdW semiconductors. Authors acknowledge the NSF DMR project No. 2205973 “Controlling Electron, Magnon, and Phonon States in Quasi‐2D Antiferromagnetic Semiconductors for Enabling Novel Device Functionalities” and NSF MRI project No. 2019056 “Development of a Cryogenic Integrated Micro-Raman-Brillouin-Mandelstam Spectrometer.”
In this invited contribution, we review recent results and report on the phase transitions and de-pinning of the charge-density waves in single-crystal 1T-TaS2 thin-film and 1T-TaS2 / h-BN heterostructure devices. It is known that 1T-TaS2 reveals charge-density-wave phases below and above room temperature. The de-pinning of the charge-density waves in the quasi-2D materials is different from that in “conventional” bulk charge-density-wave materials with quasi-1D motifs in the crystal structure. The de-pinning process in 1T-TaS2 is not accompanied by an observable abrupt increase in electric current – in contrast to de-pinning in the conventional charge-density-wave materials with the quasi-1D crystal structure. The obtained results contribute to the development of the charge-density-wave devices for applications in electronics and optoelectronics.
We report the results of an experimental study that compares the performance of graphene and boron nitride flakes as
fillers in the thermal interface materials. The thickness of both fillers varied from a single atomic plane to about a
hundred. The measurements have been conducted using a standard TIM tester. Our results show that the addition of a
small fraction of graphene (f=4 wt%) to a commercial thermal interface material increases the resulting apparent thermal
conductivity substantially stronger than the addition of boron nitride. The obtained data suggest that graphene and fewlayer
graphene flakes couple better to the matrix materials than the boron nitride fillers. A combination of both fillers can
be used to increase the thermal conductivity while controlling the electrical conduction.
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