Сегодня в 15:00 состоится семинар Центра Квантовых Метаматериалов (НИУ ВШЭ)на тему "Atomic collapse and pseudo-magnetic fields in graphene"
Докладчик: François Peeters, Universiteit Antwerpen, Belgium
Аннотация: The relativistic wave equation for the electron, derived by Paul Dirac in 1928, predicts that heavy atoms will undergo atomic collapse. Electronic states sink into the positron continuum triggering the spontaneous creation of electron-positron pairs. The extremely high charge requirements have prevented the observation of this phenomenon. However, thanks to the relativistic nature of the carriers and no energy gap in graphene, the same physics can be observed at a much lower scale. We discuss the atomic collapse analogue in graphene and its experimental realization using artificial nuclei. The required supercritical charge may be created via the deposition of impurities on the surface of graphene or using charged vacancies. These artificial nuclei trap electrons in a sequence of quasi-bound states. Experimentally, these supercritical states can be observed as resonances in the local density of states close to the charge center.
Two-dimensional (2D) atomic crystals placed on an atomically flat substrate can be forced to undergo a buckling transition, which results in periodically strained superlattices. Such lateral superlattices in graphene lead to a periodically modulated pseudo-magnetic field, which in turn creates a post-graphene material with flat electronic bands. Bringing the Fermi level into the flat band by electrostatic doping shows the opening of a pseudogap feature in the electronic spectrum indicative of emergent correlated states.
Talk is based on:
Jinhai Mao, Yuhang Jiang, Dean Moldovan, Guohong Li, Kenji Watanabe, Takashi Taniguchi, Massoud
Ramezani Masir, Francois M. Peeters, and Eva Y. Andrei: Realization of a Tunable Artificial Atom at a Charged Vacancy in Graphene, Nature Physics 12, 545-550 (2016).
Yuhang Jiang, Jinhai Mao, Dean Moldovan, Massoud Ramezani Masir, Guohong Li, Kenji Watanabe,
Takashi Taniguchi, Francois M. Peeters and Eva Y. Andrei: Tuning a Circular p-n Junction in Graphene from Quantum Confinement to Optical Guiding, Nature Nanotechnology 12, 1045-1050 (2017).
Mao Jinhai, Milovanovic Slavisa, Andelkovic Misa, Lai Xinyuan, Cao Yang, Watanabe Kenji, Taniguchi Takashi, Covaci Lucian, Peeters Francois, Geim Andre, Jiang Yuhang, Andrei Eva: Evidence of flat bands and correlated states in buckled graphene superlattices, Nature 584, 7820 (2020).