First-Principles Study of Carrier-Mediated and Vacancy-Induced Ferromagnetism in Molybdenum Disulfide Monolayer

We have investigated the magnetic properties of semiconducting molybdenum disulfide (MoS2) monolayer (ML) using the plane wave self-consistent field (PWscf) method within the framework of density functional theory (DFT). The pristine semiconducting bulk MoS2 is nonmagnetic (NM), due to the spin pairing of two electrons. We have indicated that the carrier-mediated ferromagnetism is available on the MoS2 ML as both the hole and electron carriers. The ordinary neutral S (VS0) vacancy creates the localized vacancy defect level and this level does not create the ferromagnetic (FM) state due to the spin pairing of two electrons by three Mo dangling bonds. While we have shown that the FM state is possible to create the FM state, due to the additional hole and electron carriers on the valency band and localized vacancy defect level by positively and negatively charged S (VS1+ and VS1- ) and positively charged Mo (VMo1+) vacancies.

The spin pairing symmetry of d-wave superconductor indicated by tunneling spectroscopy

Andreev reflection on the interface of ferromagnet/superconductor ([Formula: see text]) junction provides a tool for exhibiting the spin pairing symmetry in superconductors. The triplet tunneling in [Formula: see text]-wave [Formula: see text] junction observed in recent experiments revived a fundamental interest: the pairing mechanism of the superconducting cuprate. Here we show that in a doped cuprate, the effective spin coupling between the doped holes on the O sites yields a symmetric bound pair state [Formula: see text] with quantum numbers [Formula: see text], [Formula: see text] in the CuO2 layer, which explains the origin of the resonating valence bound state in cuprates, as well as the tunneling experiments. In addition, the [Formula: see text]-wave is consistent with the triplet pairing since the observable orbital wavefunction is a projection from the total odd-frequency wavefunction onto the quasi-2D superconducting CuO[Formula: see text] layer. High-temperature superconductivity as a long-standing puzzle touches upon a hiding symmetry: the triplet state ([Formula: see text], [Formula: see text]) is indistinguishable from the singlet ([Formula: see text]) either in NMR measurements, or in muon detections, but can be identified by tunneling spectroscopy of [Formula: see text] junction.