Molecularly-linked gold nanoparticle films across the insulator-to-metal transition: from hopping to strong electron correlationsMonique Tie (Postdoctoral researcher)Department of ChemistryUniversity of Toronto

Abstract: Strong electron-electron interactions are widely believed to play a key role in a range of remarkable phenomena such as high Tc superconductivity among others. Strongly correlated electrons are often described by the Hubbard model, which captures important gross features of phase diagrams of strongly correlated materials. However, open challenges include experimentally mapping correlated electron phenomena beyond those captured by the Hubbard model.

We use both film thickness and electrolyte gating to study a metal-insulator transition in a new class of strongly correlated material, namely, nanostructured materials, using 1,4-butanedithiol-linked gold nanoparticle films (NPFs) as an example. On the insulating side of the transition, we observe Efros-Shklovskii variable range hopping and a soft Coulomb gap, evidencing the importance of Coulomb barriers. On the metallic side of the transition, we observe signatures of strong disorder mediated electron-electron correlations. Films near the metal-insulator transition also reveal a zero-bias conductance peak, which we attribute to a resonance at the Fermi level predicted by the Hubbard and Anderson impurity models when electrons delocalize and experience strong Coulomb electron-electron interactions.

This study shows that by enabling large changes in carrier density, electrolyte gating of gold NPFs is a powerful means for tuning through the Hubbard MIT in NPFs. By revealing the range of behaviours that strongly correlated electrons can exhibit, this platform can guide the development of an improved understanding of correlated materials.

Bio: Postdoctoral researcher in the Dhirani's group.

Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et de Génie physique de la Polytechnique.