Imaging and Spectroscopy of Individual Paramagnetic Electronic States on the Atomic Scale

Paramagnetic point defects are among the most coherent qubits founiture¹. Using these systems for quantum applications will require detection and readout of single electrically isolated paramagnetic states with atomic scale spatial resolution that provides independent addressability of spin qubits. The spatial resolutions of various electrical², optical³ and even scanning probe based single spin detection techniques⁴ are still either well above the atomic scale or require conducting substrates in which fluctuating charges can induce significant decoherence. Thus, a reliable single-spin detection technique with atomic scale resolution and access to individually isolated qubit states is needed.

The particular focus of the work presented here is the development of a single-spin magnetic resonance microscopy technique with atomic scale resolution that is based on spin-dependent single electron tunneling. A brief conceptual overview about the concept of this single-spin magnetic resonance tunneling force microscopy is presented, which is proposed to observe the spin-manifold of individual defects through detection of random telegraph noise produced by spin-dependent tunneling into and out of a probe state⁵. While this microscope has not been demonstrated yet, several milestones for its implementation have been achieved. In particular, it has been demonstrated:

1. That silicon dangling bonds (so called E' centers) have a suitable spin-dynamics for their utilization as spin-readout probes for the investigated spin-microscopy concept⁶;
2. That magnetic resonance based in-situ vector magnetometry in a low-temperature ultra-high vacuum scanning-probe setup is possible and this can be used to establish well-controlled magnetic resonance conditions to the investigated samples;
3. That the detection and imaging of individual phosphorous donor atoms, individual surface defect states, as well as charge currents that percolate through these states is possible under appropriate tip-to-sample bias conditions⁷;
4. That random telegraph noise of the Coulomb forces caused by individual electrons that randomly tunnel into and out highly localized surface states can be observed.

1. K. Saeedi et al., Science 342, 830 (2013);
2. A. Morello et al., Nature 467, 687 (2010);
3. A. Gruber et al., Science 276, 2012 (1997);
4. D. Rugar et al., Nature 43, 329 (2004);
5. A. Payne, K. Ambal, C. Boehme, C. C. Williams, Phys. Rev. B 91, 195433 (2015);
6. K. Ambal et al., Phys. Rev. Applied 4, 024008 (2015);
7. K. Ambal et.al., Sci. Rep. 6, 18531 (2016).

For further information please contact robert.mcmichael [at] nist.gov (Robert McMichael), 301-975-5121.