36 research outputs found
All-optical hyperpolarization of electron and nuclear spins in diamond
Low thermal polarization of nuclear spins is a primary sensitivity limitation
for nuclear magnetic resonance. Here we demonstrate optically pumped
(microwave-free) nuclear spin polarization of and
in -doped diamond.
polarization enhancements up to above thermal equilibrium are observed
in the paramagnetic system . Nuclear spin polarization is
shown to diffuse to bulk with NMR enhancements of at
room temperature and at , enabling a route to
microwave-free high-sensitivity NMR study of biological samples in ambient
conditions.Comment: 5 pages, 5 figure
Optical properties and Zeeman spectroscopy of niobium in silicon carbide
The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor
Exhaustive characterization of Si vacancy complex in 4H-SiC
The negatively charged silicon vacancy () in silicon
carbide is a well-studied point defect for quantum applications. At the same
time, a closer inspection of ensemble photoluminescence and electron
paramagnetic resonance measurements reveals an abundance of related but so far
unidentified signals. In this study, we search for defects in 4H-SiC that
explain the above magneto-optical signals in a defect database generated by
Automatic Defect Analysis and Qualification (ADAQ) workflows. This search
reveals only one class of atomic structures that exhibit silicon-vacancy-like
properties in the data: a carbon antisite () within
sub-nanometer distances from the silicon vacancy only slightly alters the
latter without affecting the charge or spin state. Such perturbation is
energetically bound. We consider the formation of up
to 2 nm distance and report their zero phonon lines and zero field splitting
values. In addition, we performed high-resolution photoluminescence experiments
in the silicon vacancy region and found an abundance of lines. Comparing our
computational and experimental results, several configurations show great
agreement. Our work demonstrates the effectiveness of a database with
high-throughput results in the search for defects in quantum applications
Exhaustive characterization of modified Si vacancies in 4H-SiC
The negatively charged silicon vacancy VSi− in silicon carbide is a well-studied point defect for quantum applications. At the same time, a closer inspection of ensemble photoluminescence and electron paramagnetic resonance measurements reveals an abundance of related but so far unidentified signals. In this study, we search for defects in 4H-SiC that explain the above magneto-optical signals in a defect database generated by automatic defect analysis and qualification (ADAQ) workflows. This search reveals only one class of atomic structures that exhibit silicon-vacancy-like properties in the data: a carbon antisite (CSi) within sub-nanometer distances from the silicon vacancy only slightly alters the latter without affecting the charge or spin state. Such a perturbation is energetically bound. We consider the formation of VSi−+CSi up to 2 nm distance and report their zero phonon lines and zero field splitting values. In addition, we perform high-resolution photoluminescence experiments in the silicon vacancy region and find an abundance of lines. Comparing our computational and experimental results, several configurations show great agreement. Our work demonstrates the effectiveness of a database with high-throughput results in the search for defects in quantum applications
Exploiting ionization dynamics in the nitrogen vacancy center for rapid, high-contrast spin, and charge state initialization
We propose and experimentally demonstrate a method to strongly increase the sensitivity of spin measure-ments on nitrogen vacancy (NV) centers in diamond, which can be readily implemented in existing quantum sensing experiments. While charge state transitions of this defect are generally considered a parasitic effect to be avoided, we show here that these can be used to significantly increase the NV centers spin contrast, a key quantity for high-sensitivity magnetometry and high-fidelity state readout. The protocol consists of a two-step procedure, in which the charge state of the defect is first purified by a strong laser pulse, followed by weak illumination to obtain high spin polarization. We observe a relative improvement of the readout contrast by 17% and infer a reduction of the initialization error of more than 50%. The contrast enhancement is accompanied by a beneficial increase of the readout signal. For long sequence durations, typically encountered in high-resolution magnetometry, a measurement speedup by a factor of &gt;1.5 is extracted, and we find that the technique is beneficial for sequences of any duration. Additionally, our findings give detailed insight into the charge and spin polarization dynamics of the NV center and provide actionable insights for direct optical, spin-to-charge, and electrical readout of solid-state spin centers.Funding Agencies|Austrian Science Fund (FWF) [G0A0520N, 101038045]; European Unions Horizon 2020 and Horizon Europe research and innovation programs; National Research, Development and Innovation Office in Hungary (NKFIH); EU QuantERA II MAESTRO project; Quantum Information National Laboratory via the Ministry of Culture and Innovation of Hungary; MTA Premium Postdoctoral Research Program; Knut and Alice Wallenberg Foundation through the WBSQD2 project; National Research, Development and Innovation Office in Hungary (NKFIH); FWO (Funds for Scientific Research) Flanders; European Unions Horizon 2020 research and innovation program; [I 3167-N27 SiC-EiC]; [864036]; [870002]; [877615]; [101046911]; [KKP129866]; [2018.0071]; [FK 137918]; [G0D1721N]</p