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TT: Fachverband Tiefe Temperaturen

TT 43: Focus Session: Spin Phenomena in Chiral Molecular Systems II (joint session O/TT)

TT 43.2: Topical Talk

Wednesday, March 20, 2024, 11:00–11:30, MA 141

Chirality-induced spin selectivity at the single-molecule scale — •Daniel Emil Bürgler1, Mohammad Reza Safari1, Frank Matthes1, Nicolae Atodiresei1, Claus Michael Schneider1, and Karl-Heinz Ernst21Peter Grünberg Institut, Forschungszentrum Jülich, Germany — 2Molecular Surface Science Group, Empa, Dübendorf, Switzerland

Chirality-induced spin selectivity (CISS) leads to spin-selective electron transport in chiral molecules and enantiospecific adsorption on magnetic surfaces. To advance the development of theoretical models, well-defined single-molecule experiments are needed. Here, we report CISS effects for single chiral heptahelicene molecules that are sublimed under ultra-high vacuum onto uncoated single-crystalline and perpendicularly magnetized Co nanoislands. We use spin-polarized scanning tunneling microscopy (SP-STM) to (i) determine the handedness of individual heptahelicenes and the magnetization direction of the underlying Co nanoisland and (ii) measure spin-polarized transport through single molecules. Analysis of more than 740 molecules provides unequivocal evidence for enantioselective adsorption and reveals that enantioselection must occur in a physisorbed transient precursor state. IV curves of two enantiomers under otherwise identical conditions show at 5 K magnetochiral conductance asymmetries of up to 50% when either the molecular handedness is exchanged or the magnetization of the STM tip or Co substrate is reversed. The results demonstrate that CISS is a single-molecule effect and rule out electron-phonon coupling and ensemble effects as its primary mechanisms.

Keywords: Chirality-induced spin selectivity; Enantiospecific adsorption; Magnetic surfaces; Spin transport; Scanning tunneling microscopy

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