Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.02040v1</id>\n    <title>On-surface synthesis and aromaticity of large cyclocarbons</title>\n    <updated>2026-03-02T16:24:29Z</updated>\n    <link href='https://arxiv.org/abs/2603.02040v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.02040v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>Molecular rings of N carbon atoms, that is, cyclo[N]carbons, or $C_N$, can be formed by tip-induced chemistry [1-7]. Because of their monocyclic geometry, cyclocarbons are fundamentally important for testing theoretical models of aromaticity [8-11]. Here, we synthesized large cyclo[N]carbons, with N up to 88, by tip-induced chemistry on a NaCl surface and studied their aromaticity by measuring their transport gaps by scanning tunnelling spectroscopy. We first generated $C_{20}$ and $C_{22}$, and then fused multiple cyclocarbons [5-7] by means of atom manipulation, obtaining $C_{42}$, $C_{44}$, $C_{46}$, $C_{66}$ and $C_{88}$. In line with theory, using a finely tuned density functional approximation [12-15], we observe a substantially smaller transport gap for $C_{20}$ (N = 4n) compared to $C_{22}$ (4n+2), and for $C_{44}$ (4n) compared to $C_{42}$ (4n+2). In larger cyclocarbons, the oscillation of the transport gap between anti-aromatic N = 4n and aromatic N = 4n+2 cyclocarbons becomes smaller, and is expected to eventually vanish with increasing N indicating non-aromaticity. Our experimental results show that aromaticity persists at N = 42, and theory predicts ring currents comparable in magnitude to that of benzene in cyclocarbons of this size. In the future, large cyclocarbons could be used as model systems to study conductance, quantum interference, and the effects of aromaticity in single atomic carbon wires and circuits.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='cond-mat.mes-hall'/>\n    <published>2026-03-02T16:24:29Z</published>\n    <arxiv:comment>56 pages, including Supplemental Information</arxiv:comment>\n    <arxiv:primary_category term='cond-mat.mes-hall'/>\n    <author>\n      <name>Lisanne Sellies</name>\n    </author>\n    <author>\n      <name>Marco Vitek</name>\n    </author>\n    <author>\n      <name>Yueze Gao</name>\n    </author>\n    <author>\n      <name>Fabian Paschke</name>\n    </author>\n    <author>\n      <name>Florian Albrecht</name>\n    </author>\n    <author>\n      <name>Jakob Eckrich</name>\n    </author>\n    <author>\n      <name>Beren Dempsey</name>\n    </author>\n    <author>\n      <name>Leonard-Alexander Lieske</name>\n    </author>\n    <author>\n      <name>Harry L. Anderson</name>\n    </author>\n    <author>\n      <name>Igor Rončević</name>\n    </author>\n    <author>\n      <name>Leo Gross</name>\n    </author>\n  </entry>"
}