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Physics Department presents Novel nano-imaging techniques for probing electronic properties in graphene devices

February 20 @ 12:00 pm 1:00 pm

Presented by:

Dr. Dorri Halbertal

Columbia University

My talk will present results of two studies of heat dissipation related processes in graphene devices, involving unconventional local probe techniques. The first part of my talk will focus on my work at the Weizmann Institute involving the developed of a scanning nanoSQUID with sub 50 nm diameter that resides at the apex of a sharp pipette [1] acting simultaneously as nanomagnetometer with single spin sensitivity and as nano-thermometer providing cryogenic thermal imaging with four orders of magnitude improved thermal sensitivity of below 1 μK/Hz1/2 [2]. Using this scanning nano-thermometry we visualized and controlled phonon emission due to inelastic electron scattering off individual atomic defects in graphene [3]. The inferred electron- phonon “cooling power spectrum” exhibits sharp peaks when the Fermi level comes into resonance with electronic quasi-bound states at such defects, a hitherto uncharted process. The atomic defects are very rare in the bulk but abundant at the edges, acting as switchable atomic- scale phonon emitters that establish the dominant dissipation mechanism in graphene. The second part of my talk will focus on a work in progress at Columbia University, involving the study of domain walls in twisted bi-layer graphene using a local photo-thermal current imaging technique, providing a mean to probe the inner structure of the domain wall in this interesting system.

[1] Vasyukov et al., Nature Nanotech. 8, 639 (2013).
[2] D. Halbertal, J. Cuppens, M. Ben Shalom, L. Embon, N. Shadmi, Y. Anahory, H. R. Naren, J. Sarkar, A. Uri, Y. Ronen, Y. Myasoedov, L. S. Levitov, E. Joselevich, A. K. Geim, and E. Zeldov, Nature 539, 407 (2016).
[3] D. Halbertal, M. Ben Shalom, A. Uri, K. Bagani, A.Y. Meltzer, I. Marcus, Y. Myasoedov, J. Birkbeck, L.S. Levitov, A.K. Geim, and E. Zeldov, Science 358, 1303-1306 (2017).