---

The combination of electron spin resonance and scanning tunneling microscopy drastically widened the range of interactions that can be studied on the atomic scale [1]. Overcoming the energy resolution of typical scanning tunneling spectroscopy by 3 orders of magnitude, it has been used to characterize both dipolar and exchange interactions between single spins [2], tune their level of entanglement [3] and even resolve the hyperfine interaction of single atomic spins [4]. In this talk I will first discuss how studying the anisotropy of the hyperfine interaction can be used to determine the electronic ground state of TiH/MgO/Ag(100), a feature that so far eluded experimentalists [5]. The second part of the talk will be devoted to the study of dynamics of atomic spins. We first demonstrate that a DC-pump-probe scheme can be used to study the free evolution of two coupled atomic spins: by controlling their level of entanglement, we find a tuning point in which a spin excitation is swapped back and forth between them [6]. This is then used as the basis for a larger study of the free propagation of spin excitations within atomic chains and quasi-2D structures [7]. Finally, I will discuss our most recent experiment in which the size of the system is reduced to a single atom: using the same technique we intend to gain insight into the dynamics between a single electron and a nuclear spin mediated via the hyperfine interaction [8]. [1] Baumann et al., Science 350, 6259 (2015) [2] Choi et al., Nat. Nano 12, (2017) [3] Yang et al., Phys. Rev. Lett. 119, 227206 (2017) [4] Willke et al., Science 362 (2018) [5] Farinacci, et al., Nano Letters 22, 8470 (2022) [6] Veldman et al., Science 372, 6545 (2021) [7] Veldman et al., in preparation [8] Veldman et al., in preparation

---

Laetitia Farinacci, FU Berlin
Seminar Room of the Institute of Physics II
Contact: Erwann Bocquillon