Cascade of phase transitions and Dirac revivals in magic-angle graphene
| Autor: | Uri Zondiner, Kenji Watanabe, Yuan Cao, Daniel Rodan-Legrain, F. von Oppen, Yuval Oreg, Asaf Rozen, Ady Stern, Erez Berg, Shahal Ilani, Pablo Jarillo-Herrero, Raquel Queiroz, Takashi Taniguchi |
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| Rok vydání: | 2020 |
| Předmět: |
Phase transition
Electronic properties and materials Magic angle Population FOS: Physical sciences 02 engineering and technology 01 natural sciences law.invention Condensed Matter - Strongly Correlated Electrons law Mesoscale and Nanoscale Physics (cond-mat.mes-hall) 0103 physical sciences Symmetry breaking 010306 general physics education Superconductivity Physics education.field_of_study Multidisciplinary Strongly Correlated Electrons (cond-mat.str-el) Condensed Matter - Mesoscale and Nanoscale Physics 500 Naturwissenschaften und Mathematik::530 Physik::539 Moderne Physik Condensed matter physics Graphene 021001 nanoscience & nanotechnology Electronic properties and devices 0210 nano-technology Bilayer graphene Spontaneous magnetization |
| Zdroj: | arXiv Nature |
| ISSN: | 1476-4687 0028-0836 |
| DOI: | 10.1038/s41586-020-2373-y |
| Popis: | Twisted bilayer graphene near the magic angle exhibits remarkably rich electron correlation physics, displaying insulating, magnetic, and superconducting phases. Here, using measurements of the local electronic compressibility, we reveal that these phases originate from a high-energy state with an unusual sequence of band populations. As carriers are added to the system, rather than filling all the four spin and valley flavors equally, we find that the population occurs through a sequence of sharp phase transitions, which appear as strong asymmetric jumps of the electronic compressibility near integer fillings of the moire lattice. At each transition, a single spin/valley flavor takes all the carriers from its partially filled peers, "resetting" them back to the vicinity of the charge neutrality point. As a result, the Dirac-like character observed near the charge neutrality reappears after each integer filling. Measurement of the in-plane magnetic field dependence of the chemical potential near filling factor one reveals a large spontaneous magnetization, further substantiating this picture of a cascade of symmetry breakings. The sequence of phase transitions and Dirac revivals is observed at temperatures well above the onset of the superconducting and correlated insulating states. This indicates that the state we reveal here, with its strongly broken electronic flavor symmetry and revived Dirac-like electronic character, is a key player in the physics of magic angle graphene, forming the parent state out of which the more fragile superconducting and correlated insulating ground states emerge. 42 pages, 22 figures |
| Databáze: | OpenAIRE |
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