13C dynamic nuclear polarization in diamond via a microwave-free ?integrated? cross effect

J. HENSHAW; D. PAGLIERO; P.R. ZANGARA; M.B. FRANZONI; A. AJOY; R.H. ACOSTA; J. REIMER; A. PINES; C.A. MERILES

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Lugar: Washington DC, USA; Año: 2019

0027-8424

Color-center-hosting semiconductors are emerging aspromising source materials for low-field dynamic nuclearpolarization (DNP) at or near room temperature, buthyperfine broadening, susceptibility to magnetic fieldheterogeneity, and nuclear spin relaxation induced by otherparamagnetic defects set practical constraints difficult tocircumvent. Here, we explore an alternate route to colorcenter-assisted DNP using nitrogen-vacancy (NV) centers indiamond coupled to substitutional nitrogen impurities, theso-called P1 centers. Working near the level anti-crossingcondition ? where the P1 Zeeman splitting matches one ofthe NV spin transitions ? we demonstrate efficientmicrowave-free 13C DNP through the use of consecutivemagnetic field sweeps and continuous optical excitation. Theamplitude and sign of the polarization can be controlled byadjusting the low-to-high and high-to-low magnetic fieldsweep rates in each cycle so that one is much faster than theother. By comparing the 13C DNP response for differentcrystal orientations, we show that the process is robust tomagnetic field/NV misalignment, a feature that makes thepresent technique suitable to diamond powders and settingswhere the field is heterogeneous. Applications to shallowNVs could capitalize on the greater physical proximitybetween surface paramagnetic defects and outer nuclei toefficiently polarize target samples in contact with thediamond crystal.