Tunable Magnetic Coupling in Graphene Nanoribbon Quantum Dots

Peter H Jacobse; Mamun Sarker; Anshul Saxena; Percy Zahl; Ziyi Wang; Emma Berger; Narayana R Aluru; Alexander Sinitskii; Michael F Crommie

doi:10.1002/smll.202400473

Tunable Magnetic Coupling in Graphene Nanoribbon Quantum Dots

Small. 2024 Feb 27:e2400473. doi: 10.1002/smll.202400473. Online ahead of print.

Authors

Peter H Jacobse¹, Mamun Sarker^{2

3}, Anshul Saxena^{4

5}, Percy Zahl⁶, Ziyi Wang^{1

7

8}, Emma Berger¹, Narayana R Aluru^{4

5}, Alexander Sinitskii^{2

3}, Michael F Crommie^{1

7

8}

Affiliations

¹ Department of Physics, University of California, Berkeley, Berkeley, CA, 94720, USA.
² Department of Chemistry, University of Nebraska, Lincoln, NE, 68588, USA.
³ Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
⁴ Walker Department of Mechanical Engineering, University of Texas, Austin, TX, 78712, USA.
⁵ Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX, 78712, USA.
⁶ Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁷ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁸ Kavli Energy NanoSciences Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.

PMID: 38412424
DOI: 10.1002/smll.202400473

Abstract

Carbon-based quantum dots (QDs) enable flexible manipulation of electronic behavior at the nanoscale, but controlling their magnetic properties requires atomically precise structural control. While magnetism is observed in organic molecules and graphene nanoribbons (GNRs), GNR precursors enabling bottom-up fabrication of QDs with various spin ground states have not yet been reported. Here the development of a new GNR precursor that results in magnetic QD structures embedded in semiconducting GNRs is reported. Inserting one such molecule into the GNR backbone and graphitizing it results in a QD region hosting one unpaired electron. QDs composed of two precursor molecules exhibit nonmagnetic, antiferromagnetic, or antiferromagnetic ground states, depending on the structural details that determine the coupling behavior of the spins originating from each molecule. The synthesis of these QDs and the emergence of localized states are demonstrated through high-resolution atomic force microscopy (HR-AFM), scanning tunneling microscopy (STM) imaging, and spectroscopy, and the relationship between QD atomic structure and magnetic properties is uncovered. GNR QDs provide a useful platform for controlling the spin-degree of freedom in carbon-based nanostructures.

Keywords: Quantum dots; graphene nanoribbons; magnetism; spin.

Abstract

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