Fractional quantum Hall phase transitions and four-flux states in graphene.
Phys Rev Lett
; 111(7): 076802, 2013 Aug 16.
Article
in En
| MEDLINE
| ID: mdl-23992076
ABSTRACT
Graphene and its multilayers have attracted considerable interest because their fourfold spin and valley degeneracy enables a rich variety of broken-symmetry states arising from electron-electron interactions, and raises the prospect of controlled phase transitions among them. Here we report local electronic compressibility measurements of ultraclean suspended graphene that reveal a multitude of fractional quantum Hall states surrounding filling factors ν=-1/2 and -1/4. Several of these states exhibit phase transitions that indicate abrupt changes in the underlying order, and we observe many additional oscillations in compressibility as ν approaches -1/2, suggesting further changes in spin and/or valley polarization. We use a simple model based on crossing Landau levels of composite fermions with different internal degrees of freedom to explain many qualitative features of the experimental data. Our results add to the diverse array of many-body states observed in graphene and demonstrate substantial control over their order parameters.
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Collection:
01-internacional
Database:
MEDLINE
Type of study:
Prognostic_studies
/
Qualitative_research
Language:
En
Journal:
Phys Rev Lett
Year:
2013
Document type:
Article
Affiliation country:
United States