Evidence of Higher Order Phonon Anharmonicity in Gray Arsenic Crystal.

Phonons play a key role in the heat transport process of quantum materials. The understanding of thermal behaviors of phonons will be beneficial for designing modern electronic devices. In this study, we utilize specific heat, Raman spectroscopy, and first-principles calculations combined with the phonon Boltzmann transport equation to explore the thermal transport of gray arsenic. Our specific heat data indicate the presence of the phonon anharmonicity at high temperature. This is further supported by temperature-dependent Raman data showing evident phonon softening and line width broadening. More interestingly, from the analysis of temperature-dependent Raman modes, we found that the four-phonon scattering process is indispensable for interpreting the line width broadening at high temperatures. Moreover, we evaluate the importance of the four-phonon scattering process in the heat transport of gray arsenic using the moment tensor potential method. Our work sheds light on the importance of a higher order phonon scattering process in heat transport of the materials with moderate thermal conductivity.

Dualistic insulator states in 1T-TaS2 crystals.

While the monolayer sheet is well-established as a Mott-insulator with a finite energy gap, the insulating nature of bulk 1T-TaS2 crystals remains ambiguous due to their varying dimensionalities and alterable interlayer coupling. In this study, we present a unique approach to unlock the intertwined two-dimensional Mott-insulator and three-dimensional band-insulator states in bulk 1T-TaS2 crystals by structuring a laddering stack along the out-of-plane direction. Through modulating the interlayer coupling, the insulating nature can be switched between band-insulator and Mott-insulator mechanisms. Our findings demonstrate the duality of insulating nature in 1T-TaS2 crystals. By manipulating the translational degree of freedom in layered crystals, our discovery presents a promising strategy for exploring fascinating physics, independent of their dimensionality, thereby offering a "three-dimensional" control for the era of slidetronics.

A broad-spectrum gas sensor based on correlated two-dimensional electron gas.

Designing a broad-spectrum gas sensor capable of identifying gas components in complex environments, such as mixed atmospheres or extreme temperatures, is a significant concern for various technologies, including energy, geological science, and planetary exploration. The main challenge lies in finding materials that exhibit high chemical stability and wide working temperature range. Materials that amplify signals through non-chemical methods could open up new sensing avenues. Here, we present the discovery of a broad-spectrum gas sensor utilizing correlated two-dimensional electron gas at a delta-doped LaAlO3/SrTiO3 interface with LaFeO3. Our study reveals that a back-gating on this two-dimensional electron gas can induce a non-volatile metal to insulator transition, which consequently can activate the two-dimensional electron gas to sensitively and quantitatively probe very broad gas species, no matter whether they are polar, non-polar, or inert gases. Different gas species cause resistance change at their sublimation or boiling temperature and a well-defined phase transition angle can quantitatively determine their partial pressures. Such unique correlated two-dimensional electron gas sensor is not affected by gas mixtures and maintains a wide operating temperature range. Furthermore, its readout is a simple measurement of electric resistance change, thus providing a very low-cost and high-efficient broad-spectrum sensing technique.

Coexistence of the hourglass and nodal-line dispersions in Nb3SiTe6 revealed by ARPES.

The non-symmorphic crystal symmetry protection in the layered topological semimetal Nb3SiTe6 can generate exotic band crossings. Herein, high-quality Nb3SiTe6 single crystal was synthesized via chemical vapor transport. The lattice structure of Nb3SiTe6 was characterized by scanning transmission electron microscopy, X-ray diffraction, core-level photoemission, and Raman spectroscopies. Angle-resolved photoemission spectroscopy was used to reveal its topological properties by presenting band structures along different high-symmetry directions. Our data show that nontrivial band features coexist in Nb3SiTe6, including an hourglass-type dispersion formed by two bands along the S-R high-symmetry line, two node lines along the S-X path and the S-R-U path, respectively. These results provide a context for the understanding and exploration of the exotic topological properties of Nb3SiTe6.