High-Precision Angle-Resolved Magnetometry with Uniaxial Quantum Centers in Silicon Carbide

Abstract

We show that uniaxial color centers in silicon carbide with hexagonal lattice structure can be used to measure not only the strength but also the polar angle of the external magnetic field with respect to the defect axis with high precision. The method is based on the optical detection of multiple spin resonances in the silicon vacancy defect with quadruplet ground state. We achieve a perfect agreement between the experimental and calculated spin resonance spectra without any fitting parameters, providing angle resolution of a few degrees in the magnetic field range up to several millitesla. Our approach is suitable for ensembles as well as for single spin-3/2 color centers, allowing for vector magnetometry on the nanoscale at ambient conditions. PACS numbers: 76.30. Mi, 71.70.Ej, 76.70.Hb, 61.72.jd Optically addressable atomic-scale spin centers constitute the basis for nanomagnetometry with high sensitivity and high spatial resolution [1,2]. The most prominent example is the nitrogen-vacancy (NV) defect in diamond and several benchmark experiments have been performed using this system [3][4][5], including proton nuclear magnetic resonance on the nanometer scale [6,7]. The principle of magnetometry with spin-carrying color centers is based on optical detection of magnetic resonance (ODMR), subject to external magnetic field. In case of individual NV defects with spin S = 1, the projection of the magnetic field on the defect axis is measured. The NV defect in the diamond cubic lattice is oriented along one out of four 111 crystallographic axes and, therefore, using ensemble experiments the magnetic field vector B can be reconstructed [8,9]. Ensembles of the NV defects are also suggested for the implementation of high precision magnetic field sensors with femtotesla sensitivity [10,11] and solid-state frequency standards [12]. These implementations require high homogeneity of the NV centers. The NV defects can be fabricated with preferential alignment [13,14], and using nonlinear shift of the ODMR lines in relatively high magnetic fields of several tens of millitesla the transverse field component can be reconstructed [15]. However, in many demanding applications much lower magnetic fields should be detected, and the information on the magnetic field orientation is difficult to extract in this approach.Here, we demonstrate an alternative approach to implement vector magnetometry for magnetic fields below several millitesla, which is suitable for ensemble as well as for individual uniaxial spin centers with S = 3/2 [16]. As a model system, we consider a silicon vacancy (V Si ) in silicon carbide (SiC) [17][18][19][20]. Due to the polymorphism of SiC, there is a large variety of vacancy-related defects with appealing quantum properties [16,[21][22][23][24][25][26][27][28][29][30][31][32][33]. All experiments presented here have been performed at room temperature on a 4H-SiC bulk crystal, possessing hexagonal lattice structure. The crystal has been grown by the standard sublimation technique, such that the [0001]...

Vector Magnetometry Using Silicon Vacancies in4H-SiC Under Ambient Conditions

“…However, only partial orientation information can be extracted for spin systems with uniaxial symmetry, as spin transition frequencies do not show azimuthal dependence [7,31]. Therefore, one is limited to sense only inclination or amplitude [7,8,31,32]. Both the NV center in diamond and V Si in hexagonal polytypes, e.g., 4H-and 6H-SiC, and a rhombic polytype, e.g., 15R-SiC, have the C 3V uniaxial symmetry, thus only allowing the detection of the polar angle of the applied field [7,8,31,32].…”

“…In order to circumvent this problem, one must apply reference fields [8,10]. The C 3V symmetry and the single preferential spin orientation of the V Si in SiC hinder genuine vector magnetometry since only the polar angle can be obtained [31,32]. However, the preferential alignment allows an unambiguous assignment of the observed resonance transitions while overlap of several resonance transitions from different NV orientations [33][34][35] adds complexity in experiments [36] and limits precision of sensing.…”

“…Therefore, one is limited to sense only inclination or amplitude [7,8,31,32]. Both the NV center in diamond and V Si in hexagonal polytypes, e.g., 4H-and 6H-SiC, and a rhombic polytype, e.g., 15R-SiC, have the C 3V uniaxial symmetry, thus only allowing the detection of the polar angle of the applied field [7,8,31,32]. The four different NV orientations in diamond allow a full reconstruction of field vectors, but this method requires one to discriminate up to 24 possible orientations since one cannot find which transition belongs to which orientation [8].…”

Selective Purcell enhancement of two closely linked zero-phonon transitions of a silicon carbide color center

“…cavity coupling | Purcell enhancement | silicon carbide | point defect | photonic crystal cavity S pin-active point defects in a variety of silicon carbide (SiC) polytypes have recently elicited a great deal of interest as the basis for solid-state single-photon sources, nanoscale quantum sensing, and quantum information science (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Such color centers in SiC offer access to emission at a variety of wavelengths, ranging from visible (600-800 nm) (7) to near-IR (850-1,300 nm) (1,2,6).…”

<strong>Scalable fabrication of single silicon vacancy defect arrays in silicon carbide using focused ion beam</strong>

“…3,5,13 These remarkable properties have been exploited in many applications in quantum photonics, 9,10 and quantum metrological studies such as high sensitivity magnetic sensing 14,15 and temperature sensing. 16 The V Si defect consists of a vacancy on a silicon site which exhibits a C 3v symmetry in 4H-SiC.…”