Monolayer graphene at charge neutrality in a quantizing magnetic field is a quantum Hall ferromagnet. Due to the spin and valley (near) degeneracies, there is a plethora of possible ground states. Previous theoretical work, based on a stringent ultra-short-range assumption on the symmetry-allowed interactions, predicts a phase diagram with distinct regions of spin-polarized, canted antiferromagnetic, intervalley coherent, and charge density wave order. While early experiments suggested that the system was in the canted antiferromagnetic phase at a perpendicular field, recent scanning tunneling studies universally find Kekulé bond order, and sometimes also charge density wave order. Recently, it was found that if one relaxes the stringent assumption mentioned above a phase with coexisting canted antiferromagnetic and Kekulé order exists in the region of the phase diagram believed to correspond to real samples. In this paper, starting from the continuum limit appropriate for experiments, we present the complete phase diagram of ν=0 graphene in the Hartree-Fock approximation, using generic symmetry-allowed interactions, assuming translation-invariant ground states up to an intervalley coherence. Allowing for a sublattice potential (valley Zeeman coupling), we find numerous phases with different types of coexisting order. We conclude with a discussion of the physical signatures of the various states.
|Journal||Physical Review B|
|State||Published - Mar 15 2023|
Bibliographical noteFunding Information:
S.J.D. would like to acknowledge Infosys funding for final year students. He also wants to acknowledge ICTS for its hospitality and kind support towards academic collaboration. A.D. was supported by the German-Israeli Foundation Grant No. I-1505-303.10/2019, Deutsche Forschungsgemeinschaft (DFG) Grant No. MI 658/10-2, DFG Grant No. RO 2247/11-1, DFG Grant No. EG 96/13-1, and CRC 183 (project C01). A.D. also thanks the Israel planning and budgeting committee (PBC) and the Weizmann Institute of Science, the Dean of Faculty fellowship, and the Koshland Foundation for financial support. S.R. and G.M. would like to thank the VAJRA scheme of SERB, India for its support. R.K.K. was supported in part by NSF Grant No. DMR-2026947. G.M. would like to acknowledge partial support from the U.S.-Israel Binational Science Foundation (Grant No. 2016130). G.M. and R.K.K. are grateful for the wonderful environment at the Aspen Center for Physics (NSF Grant No. PHY-1607611).
© 2023 American Physical Society.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics