Vacancy-Induced Tunable Kondo Effect in Twisted Bilayer Graphene.

Autor:	Chang Y; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA., Yi J; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA., Wu AK; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA., Kugler FB; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA., Andrei EY; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA., Vanderbilt D; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA., Kotliar G; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA.; Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA., Pixley JH; Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA.; Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA.
Jazyk:	angličtina
Zdroj:	Physical review letters [Phys Rev Lett] 2024 Sep 20; Vol. 133 (12), pp. 126503.
DOI:	10.1103/PhysRevLett.133.126503
Abstrakt:	In single sheets of graphene, vacancy-induced states have been shown to host an effective spin-1/2 hole that can be Kondo screened at low temperatures. Here, we show how these vacancy-induced impurity states survive in twisted bilayer graphene (TBG), which thus provides a tunable system to probe the critical destruction of the Kondo effect in pseudogap hosts. Ab initio calculations and atomic-scale modeling are used to determine the nature of the vacancy states in the vicinity of the magic angle in TBG, demonstrating that the vacancy can be treated as a quantum impurity. Utilizing this insight, we construct an Anderson impurity model with a TBG host that we solve using the numerical renormalization group combined with the kernel polynomial method. We determine the phase diagram of the model and show how there is a strict dichotomy between vacancies in the AA/BB versus AB/BA tunneling regions. In AB/BA vacancies, the Kondo temperature at the magic angle develops a broad distribution with a tail to vanishing temperatures due to multifractal wave functions at the magic angle. We argue that scanning tunneling microscopy in the vicinity of the vacancy can act as a probe of both the critical single-particle states and the underlying many-body ground state in magic-angle TBG.
Databáze:	MEDLINE
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