Dear colleagues and friends,
we are searching for a highly motivated PhD candidate within the DFG funded project “Quantum many body interactions in a two dimensional solid state system”. The goal is to create and use single spins in diamond (nitrogen vacancy centres, shortly NV) to control nanoscale two dimensional (2D) arrays of nuclear spins, with the final goal being the realisation of a solid state quantum simulator.
The description of the position and a link for application can be found here:
For further information feel free to contact me.
I would be very grateful if you could distribute this email to any suitable candidates of whom you are aware.
Thank you very much!
Dr. Boris Naydenov
Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Institute for Nanospectroscopy
+49 30 8062 – 41373
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.
Aufsichtsrat: Vorsitzender Dr. Volkmar Dietz, stv. Vorsitzende Dr. Jutta Koch-Unterseher
Geschäftsführung: Prof. Dr. Bernd Rech (Sprecher), Prof. Dr. Jan Lüning, Thomas Frederking
Sitz Berlin, AG Charlottenburg, 89 HRB 5583
This is the AMPERE MAGNETIC RESONANCE mailing list:
NMR web database:
Henshaw, Jacob, Daniela Pagliero, Pablo R. Zangara, María B. Franzoni, Ashok Ajoy, Rodolfo H. Acosta, Jeffrey A. Reimer, Alexander Pines, and Carlos A. Meriles. “Carbon-13 Dynamic Nuclear Polarization in Diamond via a Microwave-Free Integrated Cross Effect.” Proceedings of the National Academy of Sciences 116, no. 37 (September 10, 2019): 18334–40.
Color-center–hosting semiconductors are emerging as promising source materials for low-field dynamic nuclear polarization (DNP) at or near room temperature, but hyperfine broadening, susceptibility to magnetic field heterogeneity, and nuclear spin relaxation induced by other paramagnetic defects set practical constraints difficult to circumvent. Here, we explore an alternate route to color-center–assisted DNP using nitrogen-vacancy (NV) centers in diamond coupled to substitutional nitrogen impurities, the so-called P1 centers. Working near the level anticrossing condition—where the P1 Zeeman splitting matches one of the NV spin transitions—we demonstrate efficient microwave-free 13C DNP through the use of consecutive magnetic field sweeps and continuous optical excitation. The amplitude and sign of the polarization can be controlled by adjusting the low-to-high and high-to-low magnetic field sweep rates in each cycle so that one is much faster than the other. By comparing the 13C DNP response for different crystal orientations, we show that the process is robust to magnetic field/NV misalignment, a feature that makes the present technique suitable to diamond powders and settings where the field is heterogeneous. Applications to shallow NVs could capitalize on the greater physical proximity between surface paramagnetic defects and outer nuclei to efficiently polarize target samples in contact with the diamond crystal.
Ajoy, A., R. Nazaryan, K. Liu, X. Lv, B. Safvati, G. Wang, E. Druga, et al. “Enhanced Dynamic Nuclear Polarization via Swept Microwave Frequency Combs.” Proceedings of the National Academy of Sciences 115, no. 42 (October 16, 2018): 10576–81.
Dynamic nuclear polarization (DNP) has enabled enormous gains in magnetic resonance signals and led to vastly accelerated NMR/MRI imaging and spectroscopy. Unlike conventional cw-techniques, DNP methods that exploit the full electron spectrum are appealing since they allow direct participation of all electrons in the hyperpolarization process. Such methods typically entail sweeps of microwave radiation over the broad electron linewidth to excite DNP but are often inefficient because the sweeps, constrained by adiabaticity requirements, are slow. In this paper, we develop a technique to overcome the DNP bottlenecks set by the slow sweeps, using a swept microwave frequency comb that increases the effective number of polarization transfer events while respecting adiabaticity constraints. This allows a multiplicative gain in DNP enhancement, scaling with the number of comb frequencies and limited only by the hyperfine-mediated electron linewidth. We demonstrate the technique for the optical hyperpolarization of 13C nuclei in powdered microdiamonds at low fields, increasing the DNP enhancement from 30 to 100 measured with respect to the thermal signal at 7T. For low concentrations of broad linewidth electron radicals [e.g., TEMPO ((2,2,6,6- tetramethylpiperidin-1-yl)oxyl)], these multiplicative gains could exceed an order of magnitude.
Ajoy, Ashok, Kristina Liu, Raffi Nazaryan, Xudong Lv, Pablo R. Zangara, Benjamin Safvati, Guoqing Wang, et al. “Orientation-Independent Room Temperature Optical 13C Hyperpolarization in Powdered Diamond.” Science Advances 4, no. 5 (May 1, 2018):
Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond—a paramagnetic point defect whose spin can be optically polarized at room temperature—has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. We overcome this hurdle through the combined use of continuous optical illumination and a microwave sweep over a broad frequency range. As a proof of principle, we demonstrate our approach using powdered diamond with which we attain bulk 13C spin polarization in excess of 0.25% under ambient conditions. Remarkably, our technique acts efficiently on diamond crystals of all orientations and polarizes nuclear spins with a sign that depends exclusively on the direction of the microwave sweep. Our work paves the way toward the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization of nuclear spins in arbitrary liquids brought in contact with their surface.
Have a question?
If you have questions about our instrumentation or how we can help you, please contact us.