RESUMO
Spin defects in hexagonal boron nitride (hBN) are promising quantum systems for the design of flexible two-dimensional quantum sensing platforms. Here we rely on hBN crystals isotopically enriched with either 10B or 11B to investigate the isotope-dependent properties of a spin defect featuring a broadband photoluminescence signal in the near infrared. By analyzing the hyperfine structure of the spin defect while changing the boron isotope, we first confirm that it corresponds to the negatively charged boron-vacancy center ([Formula: see text]). We then show that its spin coherence properties are slightly improved in 10B-enriched samples. This is supported by numerical simulations employing cluster correlation expansion methods, which reveal the importance of the hyperfine Fermi contact term for calculating the coherence time of point defects in hBN. Using cross-relaxation spectroscopy, we finally identify dark electron spin impurities as an additional source of decoherence. This work provides new insights into the properties of [Formula: see text] spin defects, which are valuable for the future development of hBN-based quantum sensing foils.
RESUMO
Antiferromagnetic thin films are currently generating considerable excitement for low dissipation magnonics and spintronics. However, while tuneable antiferromagnetic textures form the backbone of functional devices, they are virtually unknown at the submicron scale. Here we image a wide variety of antiferromagnetic spin textures in multiferroic BiFeO3 thin films that can be tuned by strain and manipulated by electric fields through room-temperature magnetoelectric coupling. Using piezoresponse force microscopy and scanning NV magnetometry in self-organized ferroelectric patterns of BiFeO3, we reveal how strain stabilizes different types of non-collinear antiferromagnetic states (bulk-like and exotic spin cycloids) as well as collinear antiferromagnetic textures. Beyond these local-scale observations, resonant elastic X-ray scattering confirms the existence of both types of spin cycloids. Finally, we show that electric-field control of the ferroelectric landscape induces transitions either between collinear and non-collinear states or between different cycloids, offering perspectives for the design of reconfigurable antiferromagnetic spin textures on demand.
RESUMO
BACKGROUND: Kaposi's sarcoma herpesvirus (KSHV) causes Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease in immunocompromised patients including allograft recipients. Detection of KSHV DNA in blood, as well as host genetic polymorphisms has been found to be associated with an increased risk for KS. We investigated an association between single nucleotide polymorphisms (SNPs) in vascular endothelial growth factor A (VEGFA) gene region and KSHV viremia in kidney transplant recipients (KTR) in Saudi Arabia. METHODS: In total, 152 KTR who have survived kidney transplantation for at least 6 months were included in the study. KSHV viremia was determined by real-time polymerase chain reaction (PCR). Genotyping of SNPs in the VEGFA region was performed by PCR and direct sequencing, as well as by restriction fragment length polymorphism. RESULTS: KSHV DNA was detected in 28.9% (n = 44) of the study population. The A-allele at position C172A VEGFA gene promoter region was found to be associated with KSHV viremia (odd ratio [OR] = 4.8, P = 0.005). In addition, the G-allele at position C+405G in the 5'-untranslated region was associated with KSHV viremia in women, but not in men (OR = 3.98, P = 0.004). CONCLUSIONS: Our results suggest an association of VEGFA polymorphisms with KSHV viremia among KTR in this study population. A limitation of our study is that the results can only be predicated for patients 6 months after kidney transplantation and should be validated in another cohort with larger sample size.
