arXiv subjects

Xintao Jin

Publications and source records attributed to Xintao Jin.

3 recordsLinked to original sources

arXiv2025

Electronic structures and magnetism in van der Waals flat-band material Ni$_{3}$GeTe$_{2}$

The study of magnetism in two-dimensional materials has garnered significant interest, driven by fundamental investigations into low-dimensional magnetic phenomena and their potential for applications in spintronic devices. Through dynamical mean-field theory calculations, we demonstrate that Ni$_{3}$GeTe$_{2}$ exhibits flat-band characteristics resulting from the geometric frustration of its layered triangular lattice. These flat bands are further renormalized due to electronic correlation. Our calculations reveal that the magnetic order of Ni atoms is significantly influenced by both the Coulomb interaction and Hund's coupling, indicating that the physics of Ni atoms is situated in an intermediate region between Hundness and Mottness. Additionally, our results show that Ni atoms experience significant spin fluctuations in their local moments, maintaining paramagnetism at low temperatures. Furthermore, we investigate the effect of vacancies, finding a substantial suppression of the density of states at the Fermi level. The physical mechanisms uncovered by our study provide a comprehensive understanding of the novel properties exhibited in this material.

cond-mat.str-el↗

arXiv2025

DFT+DMFT investigation of the magnetic phase transition in the itinerant ferromagnet Fe$_{3}$GaTe$_{2}$

Finding and designing ferromagnets that operate above room temperature is crucial in advancing high-performance spintronic devices. The pioneering van der Waals (vdW) ferromagnet Fe$_{3}$GaTe$_{2}$ has extended the way for spintronic applications by achieving a record-high Curie temperature among its analogues. However, the physical mechanism of increasing Curie temperature in this material still needs to be explored. Here, we systematically investigate the electronic structures and magnetic properties of Fe$_{3}$GaTe$_{2}$ as a function of temperature using strongly correlated calculations, reconciling the dual nature of $d$-electrons with both localization and itinerant characters. Significantly, our study reveals the emergence of quasi-particle flat bands driven by many-body interactions, which enhance magnetic stability through a positive feedback mechanism. Furthermore, our results demonstrate the hybridization of these flat bands at low temperatures, indicating the possible presence of heavy fermion behavior in this system. Our findings suggest that tunable flat bands near the Fermi level may serve as a key factor in realizing materials with high magnetic transition temperatures and strong magnetic anisotropy. This research provides a promising pathway for exploring next-generation spintronic devices utilizing vdW flat band systems.

cond-mat.mtrl-sci↗

arXiv2024

Mechanism of magnetic phase transition in correlated magnetic metal: insight into itinerant ferromagnet Fe$_{3-δ}$GeTe$_2$

Developing a comprehensive magnetic theory for correlated itinerant magnets poses challenges due to the difficulty in reconciling both local moments and itinerant electrons. In this work, we investigate the microscopic process of magnetic phase transition in ferromagnetic metal Fe$_{3-δ}$GeTe$_2$. We find that Hund's coupling is crucial for establishing ferromagnetic order. During the ferromagnetic transition, we observe the formation of quasiparticle flat bands and an opposing tendency in spectral weight transfer, primarily between the lower and upper Hubbard bands, across the two spin channels. Moreover, our results indicate that one of the inequivalent Fe sites exhibits Mott physics, while the other Fe site exhibits Hund's physics, attributable to their distinct atomic environments. We suggest that ferromagnetic order reduces spin fluctuations and makes flat bands near the Fermi level more distinct. The hybridization between the distinctly flat bands and other itinerant bands offers a possible way to form heavy fermion behavior in ferromagnets. The complex interactions of competing orders drive correlated magnetic metals to a new frontier for discovering outstanding quantum states.

cond-mat.str-el↗