Solotronics is an electronics exploiting single dopants. We are able to investigate and control the behavior of individual magnetic dopants by situating them within quantum dots (QDs), as shown in the image below.

By observation of the first QD with a single cobalt ion, we have shown that PL quenching is not a problem for single dopants in QDs. This opened new perspectives for Solotronics,

   "Designing quantum dots for solotronics"
J. Kobak, T. Smoleński, M. Goryca, M. Papaj, K. Gietka, A. Bogucki, M. Koperski, J.-G. Rousset, J. Suffczyński, E. Janik, M. Nawrocki, A. Golnik, P. Kossacki, W. Pacuski,
Nature Communications 5, 3191 (2014).    Supplementary Information.
Press release: EN, PL.

   "Direct determination of zero-field splitting for single Co2+ ion embedded in a CdTe/ZnTe quantum dot",
J. Kobak, A. Bogucki, T. Smoleński, M. Papaj, M. Koperski, M. Potemski, P. Kossacki, A. Golnik, W. Pacuski,
Phys. Rev. B 97, 045305 (2018),

Interestingly, even a few magnetic ions is enough to induce efficient, spin dependent quenching effect,

   "Origin of luminescence quenching in structures containing CdSe/ZnSe quantum dots with a few Mn2+ ions",
K. Oreszczuk, M. Goryca, W. Pacuski, T. Smoleński, M. Nawrocki, P. Kossacki,
Phys. Rev. B 96, 205436 (2017).

and exactly two cobalt ions in a QD can be precisely observed and described,

   "Optical probing of the carriers-mediated coupling of the spin of two Co atoms in a quantum dot",
L. Besombes, J. Kobak, W. Pacuski,
Phys. Rev. B 109, 235302 (2024).  

Next, strain of the QD was used to induce magnetic properties of individual iron,

Reconfiguration of spin states of Fe dopant in a QD capering to bulk

   "Magnetic Ground State of an Individual Fe2+ Ion in Strained Semiconductor Nanostructure"
T. Smoleński, T. Kazimierczuk, J. Kobak, M. Goryca, A. Golnik, P. Kossacki, W. Pacuski,
Nature Communications 7, 10484 (2016).    Supplementary Information. Press release: EN, PL.

   "Fine structure of an exciton coupled to a single Fe2+ ion in a CdSe/ZnSe quantum dot",
T. Smoleński, T. Kazimierczuk, M. Goryca, W. Pacuski, and P. Kossacki,
Phys. Rev. B 96, 155411 (2017).

Further, we decided to understand better the effect of optical orientation of individual magnetic ions in new systems

   "Optical spin orientation of an individual Mn2+ ion in a CdSe/ZnSe quantum dot"
T. Smoleński, W. Pacuski, M. Goryca, M. Nawrocki, A. Golnik, P. Kossacki,
Phys. Rev. B 91, 045306 (2015).
Extended version: arXiv:1408.2928 (2014).

   "Readout of a dopant spin in the anisotropic quantum dot with a single magnetic ion",
A. Rodek, T. Kazimierczuk, A. Bogucki, T. Smoleński, W. Pacuski, P. Kossacki,
J. Phys.: Condens. Matter 31, 455301 (2019).

The next system, that we developed was a QD with a single Vanadium ion.

   "The single ion of Vanadium in an individual Quantum Dot ",
K. E. Po³czyńska, T. Kazimierczuk, P. Kossacki, W. Pacuski,
Phys. Rev. B 111, 085428 (2025).  

and the newest development is a single nickel ion in a QD:
   "Influence of local strain on the optical probing of a Ni spin in a charged self-assembled quantum dot",
K. E. Polczynska, S. Karouaz, W. Pacuski, L. Besombes,
Phys. Rev. B 112, 245301 (2025).  

In order to perform nonlinear optical experiments on individual dopants, we decided to introduced our QDs with single dopants to novel photonic systems

   "Antireflective photonic structure for coherent nonlinear spectroscopy of single magnetic quantum dots",
W. Pacuski, J.-G. Rousset, V. Delmonte, T. Jakubczyk, K. Sobczak, J. Borysiuk, K. Sawicki, E. Janik, J. Kasprzak,
Cryst. Growth Des. 17, 2987 (2017).

   "Coherent dynamics of a single Mn-doped quantum dot revealed by four-wave mixing spectroscopy",
J. Kasprzak, D. Wigger, T. Hahn, T. Jakubczyk, £. Zinkiewicz, P. Machnikowski, T. Kuhn, J.-F. Motte, W. Pacuski,
ACS Photonics 9, 1033–1041 (2022).     ,

   "Ultra-long-working-distance spectroscopy of single nanostructures with aspherical solid immersion microlenses",
A. Bogucki, £. Zinkiewicz, M. Grzeszczyk, W. Pacuski, K. Nogajewski, T. Kazimierczuk, A. Rodek, J. Suffczyński, K. Watanabe, T. Taniguchi, P. Wasylczyk, M. Potemski, P. Kossacki,
Light: Science & Applications 9, 48 (2020).       , Press release EN, PL.