VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Friday 9

› 8:30 - 9:00 (30min)
Tuning a Charge Impurity in Graphene: from Cloaking to Supercriticality
Eva Andrei  1@  
1 : Department of Physics, Rutgers University  -  Website
Dept. of Physics Rutgers University 136 Frelinghuysen Rd. Piscataway NJ 08855 -  United States

When the charge of a nucleus exceeds a critical value comparable to the inverse fine structure constant, relativistic effects cause the atomic orbitals to collapse. The physics in the critical regime is not experimentally accessible because it requires ultra-heavy nuclei which do not exist in nature. In graphene, due to the larger value of the effective fine structure constant, the critical regime could be reached for relatively modest charges. We study an artificial atom in graphene where a positively charged impurity serves as the nucleus and the electronic orbitals are defined by applying a magnetic field. Using scanning tunneling microscopy and spectroscopy we find that the effective charge of the impurity can be tuned from the subcritical to the supercritical regime by controlling the occupancy of the Landau levels with a gate voltage. I will show that the magnetic field makes it possible to tune the strength of impurities in graphene from subcritical to supercritical providing unprecedented access to the regime of Coulomb criticality.

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