Insulating state in tetralayers reveals an even-odd interaction effect in multilayer graphene.
Close to charge neutrality, the electronic properties of graphene and its multilayers are sensitive to electron-electron interactions. In bilayers, for instance, interactions are predicted to open a gap between valence and conduction bands, turning the system into an insulator. In mono and (Bernal-stacked) trilayers, which remain conducting at low temperature, interactions do not have equally drastic consequences. It is expected that interaction effects become weaker for thicker multilayers, whose behaviour should converge to that of graphite. Here we show that this expectation does not correspond to reality by revealing the occurrence of an insulating state close to charge neutrality in Bernal-stacked tetralayer graphene. The phenomenology-incompatible with the behaviour expected from the single-particle band structure-resembles that observed in bilayers, but the insulating state in tetralayers is visible at higher temperature. We explain our findings, and the systematic even-odd effect of interactions in Bernal-stacked layers of different thickness that emerges from experiments, in terms of a generalization of the interaction-driven, symmetry-broken states proposed for bilayers.
Department of Quantum Matter Physics (DQMP) and Group of Applied Physics (GAP), University of Geneva, 24 Quai Ernest-Ansermet, CH1211 Genéve 4, Switzerland.
Anya L
AL
Grushina
Department of Quantum Matter Physics (DQMP) and Group of Applied Physics (GAP), University of Geneva, 24 Quai Ernest-Ansermet, CH1211 Genéve 4, Switzerland.
Dong-Keun
DK
Ki
Department of Physics, Tohoku University, Sendai 980-8578, Japan.
Mikito
M
Koshino
Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, Grenoble 38042, France.
Aurelien A L
AA
Nicolet
Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, Grenoble 38042, France.
Clément
C
Faugeras
Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK.
Edward
E
McCann
Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, Grenoble 38042, France.
Marek
M
Potemski
Department of Quantum Matter Physics (DQMP) and Group of Applied Physics (GAP), University of Geneva, 24 Quai Ernest-Ansermet, CH1211 Genéve 4, Switzerland.
Alberto F
AF
Morpurgo