Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 43: Focus Session: Spins on Surfaces studied by Atomic Scale Spectroscopies IV

O 43.4: Vortrag

Mittwoch, 20. März 2024, 11:15–11:30, MA 004

Paramagnetic resonance of individual organic molecules driven by quantum spin torque — •Stepan Kovarik¹, Richard Schlitz^{1, 2}, Aishwarya Vishwakarma¹, Dominic Ruckert¹, Pietro Gambardella¹, and Sebastian Stepanow¹ — ¹Department of Materials, ETH Zurich, Switzerland — ²Department of Physics, University of Konstanz, Germany

The transfer of angular momentum between the current of spin-polarised electrons and spins of a magnetic material, the so-called spin torque, is used to control the magnetisation of modern magnetic memory devices [1]. Spin torque has also been used to excite magnetic resonance in ferromagnetic devices. [2]. Here, we use spin torque to drive the paramagnetic resonance of a single spin in a pentacene molecule adsorbed on ultrathin MgO with a time-dependent spin current injected from the tip of a scanning tunneling microscope. This novel approach to controlling single spins complements the well-established magnetic resonance driven by a time-dependent electromagnetic field. The spin-torque-driven resonance facilitates the observation of paramagnetic resonance even in regimes where the thermal polarisation of the measured spin is low. The observed signatures provide the first experimental insights into the spin-torque-driven resonance at the quantum level, previously studied only theoretically [3]. [1]D. C. Ralph, M. D. Stiles, JMMM. 320, 1190-1216 (2008). [2]T. Chen et al., Proc. IEEE. 104, 1919-1945 (2016). [3]A. M. Shakirov et al., PRB. 99, 054434 (2019).

Keywords: Spin torque; Magnetic resonance; STM; EPR; Molecule