FLEET Seminar: Prof Nancy Sandler – Strain enhancement of Kondo effect in graphene

Strain enhancement of Kondo effect in graphene

Prof Nancy Sandler, Ohio University

All welcome! The seminar flyer can be downloaded clicking on this link

Abstract:

The study of magnetic impurities on pristine graphene and its corresponding Kondo physics, results on predictions of unusual features due to the linear vanishing density of states at the Dirac points. However, despite several attempts to uniquely identify Kondo state characteristics, conclusive experimental observation of the phenomenon remains elusive, due in part to very small Kondo temperature scales for chemical potentials near these points.

Interestingly, local deformations in graphene have been shown to produce inhomogeneous charge distributions determined by the strain field’s magnitude and spatial dependence. The connection between deformations and charge inhomogeneities was quantitatively confirmed in recent measurements of the local density of states (LDOS) via scanning tunneling microscopy (STM) in setups with mobile (tipinduced) and static (intercalated impurity) local deformations [1].

Analysis of STM images revealed local sublattice-symmetry breaking in strained regions, whereby the two carbon atoms within each unit cell are differentiated by contrasting signal intensities. Surprisingly, in the presence of these local deformations a gapless dispersion is maintained. Strain-induced density enhancements have also been reported in transport experiments through isolated folds, where charge confinement gives rise to Coulomb-blockade features across the axis of the fold [2-3].

These deformation-induced changes are expected to produce unique fingerprints in the observed Kondo temperatures for magnetic impurities positioned at different lattice sties on a strained membrane. In this talk, I will review results from our recent studies on Kondo physics on strained membranes and will discuss potential experimental observations for various impurity settings [4].

[1] A. Georgi et al, Nano Letters 17, 2240 (2017).
[2] R. Castillo-Barros et al, PRB (R) 94. 125422 (2016).
[3] Y. Wu et. al, Nano Letters 18, 64 (2018).
[4] D. Zhai and N. Sandler, arXiv:1808.08285

About the speaker:

Nancy Sandler is a Professor of Physics in the Department of Physics and Astronomy at Ohio University, Athens, Ohio, USA. She holds a Ph.D. in theoretical physics from the University of Illinois at Urbana-Champaign, and a Licenciatura en Ciencias Fisicas degree from the University of Buenos Aires, Argentina.

Sandler’s research on low-dimensional materials focuses on strong interacting regimes and non-equilibrium phenomena. She is currently the Graduate Chair of the Department of Physics and Astronomy, a board member of the Margaret Boyd Scholar Program at Ohio University, and editor of the Ohio Materials Institute (previously Nanoscale and Quantum Phenomena Institute) newsletter.