arXiv subjects

Daqiang Gao

Publications and source records attributed to Daqiang Gao.

4 recordsLinked to original sources

arXiv2026

Origin of anomalous p-type conductivity in monolayer Fe-doped MoS2

Substitutional doping effectively modulates carrier polarity of semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) like MoS2. Although Fe doping typically induces n-type conductivity in monolayer MoS2, anomalous p-type behavior has also been experimentally reported, the origin of which remains unresolved. Here, we prove that this anomalous p-type conductivity originates from defect associates formed through interactions between Fe dopants and S atoms, which consists of three Fe substituting Mo (FeMo) point defects arranged into an equilateral triangle with a central S atom, denoted as 3FeMo-S associate. Its p-type effect is directly verified through scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS) measurement, in sharp contrast to the n-type behavior induced by isolated FeMo point defects, and the conclusion is further supported by electrical transport measurements and first-principles calculations. Similar 3FeW-S associates and their p-type doping effect are also identified in monolayer Fe-doped WS2. This work resolves a longstanding controversy and highlights the critical role of defect associates in modulating properties of 2D TMDs.

cond-mat.mtrl-sci↗

arXiv2024

Tunable high Chern-number quantum anomalous Hall effect through interlayer ferromagnetic coupling in two-dimensional ferromagnet NiSbO3

The high Chern-number quantum anomalous Hall effect (QAHE) is significant and fascinating due to the presence of multiple dissipationless chiral edge states. Here, we predict that monolayer NiSbO3 possesses the Chern number C = 3, confirmed by the anomalous Hall conductance and the chiral edge states. The magnetic anisotropic energy (MAE) responsible for ferromagnetic order is 0.641 meV originating from Ni-d and Sb-p orbitals, where the contributed MAE from same spin-up channels predominates. In forward electric fields, the negative MAE makes the easy magnetization direction perpendicular to the surface, which is conducive to the realizing of high Chern-number QAHE. The simulated Curie temperature is 291 K. Intriguingly, in a bilayer, the obtained C = 6 is twice that of the monolayer, thanking to the interlayer ferromagnetic coupling. Our work offers a promising candidate for potential applications in topological quantum devices and spintronics.

cond-mat.mes-hall↗

arXiv2023

Simultaneous nonreciprocal and ultra-strong coupling in cavity magnonics

We demonstrate the simultaneous realization of nonreciprocal coupling and ultra-strong coupling in cavity magnonics. By replacing a copper cylinder with a yttrium iron garnet cylinder within the photonic crystal, we achieve an ultra-strong coupling strength of 1.18 GHz and a coupling efficiency of 10.9%. Nonreciprocal microwave transmission emerges within the photonic bandgap, due to the breaking of time-reversal symmetry through the gyromagnetic and Faraday effects. This work establishes a foundation for advanced nonreciprocal devices in hybrid cavity magnonic systems, with promising applications in quantum information processing and microwave isolation.

physics.app-ph↗

arXiv2012

g-B3N3C: a novel two-dimensional graphite-like material

A novel crystalline structure of hybrid monolayer hexagonal boron nitride (BN) and graphene is predicted by means of the first-principles calculations. This material can be derived via boron or nitrogen atoms substituted by carbon atoms evenly in the graphitic BN with vacancies. The corresponding structure is constructed from a BN hexagonal ring linking an additional carbon atom. The unit cell is composed of 7 atoms, 3 of which are boron atoms, 3 are nitrogen atoms, and one is carbon atom. It behaves a similar space structure as graphene, which is thus coined as g-B3N3C. Two stable topological types associated with the carbon bonds formation, i.e., C-N or C-B bonds, are identified. Interestingly, distinct ground states of each type, depending on C-N or C-B bonds, and electronic band gap as well as magnetic properties within this material have been studied systematically. Our work demonstrates practical and efficient access to electronic properties of two-dimensional nanostructures providing an approach to tackling open fundamental questions in bandgap-engineered devices and spintronics.

cond-mat.mes-hall↗