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Valley-Polarized Topological Phases
Valley-polarized topological phases are exotic quantum states where electrons occupy distinct momentum-space valleys with differing topological properties. Arising in materials like graphene and transition metal dichalcogenides, these phases combine valleytronics and topological physics. Here, we report a new mechanism to generate in-plane magnetization direction-dependent isolated valley carriers by preserving or breaking the mirror symmetry in a 2D system. First-principle calculations are carried out on a prototype material, W2MnC2O2 MXene, to demonstrate the mechanism. A valley-coupled topological phase transition among Weyl semimetal, valley-polarized quantum anomalous Hall insulator, and topological semimetal is observed by manipulating the in-plane magnetization directions in W2MnC2O2. Monte Carlo simulations of W2MnC2O2 show that the estimated Curie temperature is around 170 K, indicating the possibility of observing valley-polarized topological states at higher temperatures. Our finding provides a generalized platform for investigating the valley and topological physics, which is extremely important for future quantum information processing applications.
Frictional Properties of Two-Dimensional Materials
This study leverages data-driven machine learning (ML) approaches to predict the frictional properties of two-dimensional (2D) materials, which are critical for nanoscale devices. Using a curated dataset of experimentally and computationally derived friction data, the authors trained ML models such as random forests and neural networks to identify relationships between friction and material descriptors like layer thickness, electronic properties, and surface chemistry. The models achieved high predictive accuracy and provided insights into key features influencing nanoscale friction. This approach enables rapid screening of novel 2D materials for low-friction applications, reducing reliance on time-consuming experiments or simulations.
Accelerated Discovery of the Valley-Polarized Quantum Anomalous Hall Effect in MXenes
This study presents a comprehensive study on identifying two-dimensional (2D) MXene materials that exhibit the valley-polarized quantum anomalous Hall (VP-QAH) effect. We employed a high-throughput first-principles approach to systematically screen inversion symmetry-broken 2D MXenes, resulting in the identification of 14 MXenes with out-of-plane ferromagnetic ground states under spin-orbit coupling. These materials exhibit nontrivial Berry curvature and chiral edge states, confirming the presence of the VP-QAH effect. Additionally, machine learning models were developed using elemental features to accurately predict magnetic nodal line semimetal classifications and nodal positions. Our study provides a robust platform to incorporate valley and topological physics, which would accelerate the search for promising VP-QAH materials.
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