Spin and valley quantum Hall ferromagnetism in graphene

Young, Andrea; Dean, Cory; Wang, Lei; Ren, Haowen; Cadden-Zimansky, Paul; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Shepard, Kenneth L.; Kim, Philip

doi:10.1038/nphys2307

Cited by 359 publications

(490 citation statements)

References 52 publications

(67 reference statements)

Supporting

Mentioning

441

Contrasting

Unclassified

Order By: Relevance

“…Along this line the Hamiltonian commutes with ten ( S, T z , and the six Π operators) of the fifteen SU(4) generators identified in Eq. (2). The other five (T x,y , N x,y,z ) SU(4) generators form a a natural orderparameter vector space on which the SO(5) group acts.…”

Section: Hamiltonian Symmetriesmentioning

confidence: 99%

“….. The quantum Hall effect nevertheless occurs at all intermediate integer filling factors 1,2 , and at many fractional filling factors [3][4][5] , usually 6 with a broken symmetry incompressible ground state. When lattice corrections to the continuum Dirac model's Coulomb interactions are ignored the ground state at neutrality (ν = 0) is a Slater determinant 7 with all the N = 0 single-particle states of two arbitrarily chosen flavors occupied and, because the Hamiltonian is SU(4) invariant, has four independent degenerate Goldstone modes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

SO(5) symmetry in the quantum Hall effect in graphene

Sodemann

Araki

et al. 2014

Phys. Rev. B

View full text Add to dashboard Cite

Electrons in graphene have four flavors associated with low-energy spin and valley degrees of freedom. The fractional quantum Hall effect in graphene is dominated by long-range Coulomb interactions which are invariant under rotations in spin-valley space. This SU(4) symmetry is spontaneously broken at most filling factors, and also weakly broken by atomic scale valley-dependent and valley-exchange interactions with coupling constants gz and g ⊥ . In this paper we demonstrate that when gz = −g ⊥ an exact SO(5) symmetry survives which unifies the Néel spin order parameter of the antiferromagnetic state and the XY valley order parameter of the Kekulé distortion state into a single five-component order parameter. The proximity of the highly insulating quantum Hall state observed in graphene at ν = 0 to an ideal SO(5) symmetric quantum Hall state remains an open experimental question. We illustrate the physics associated with this SO(5) symmetry by studying the multiplet structure and collective dynamics of filling factor ν = 0 quantum Hall states based on exact-diagonalization and low-energy effective theory approaches. This allows to illustrate how manifestations of the SO(5) symmetry would survive even when it is weakly broken.

show abstract

Section: Hamiltonian Symmetriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

SO(5) symmetry in the quantum Hall effect in graphene

Sodemann

Araki

et al. 2014

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…23,25 also reveal a large sequence of integer QH states with ν ≥ 1. Among these, there are two states associated with quarter filling of the lowest Landau level, i.e., ν = ±1.…”

mentioning

confidence: 99%

“…From the experimental point of view, a lot of effort was devoted to revealing the underlying nature of the strongly insulating ν = 0 QH state, associated with half-filling of the lowest Landau level [13][14][15][16][17][18][19][20][21][22][23][24][25] . The main advances in resolving the nature of the QH states were made by applying a tilted magnetic field to high-quality graphene devices, that were fabricated on a thin hexagonal boron nitride substrate 23,24 or encapsulated between two layers of hexagonal boron nitride 25 .…”

mentioning

confidence: 99%

“…The main advances in resolving the nature of the QH states were made by applying a tilted magnetic field to high-quality graphene devices, that were fabricated on a thin hexagonal boron nitride substrate 23,24 or encapsulated between two layers of hexagonal boron nitride 25 . In the case of ν = 0 QH state, in particular, a careful analysis of the conductance and the bulk density of states [23][24][25] suggests that the state is not spin polarized when the magnetic field is perpendicular to the plane of graphene. This is consistent, for example, with both an antiferromagnet and a charge density wave.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Generalized Landau level representation: Effect of static screening in the quantum Hall effect in graphene

Shovkovy

Xia

2016

Phys. Rev. B

View full text Add to dashboard Cite

By making use of the generalized Landau-level representation (GLLR) for the quasiparticle propagator, we study the effect of screening on the properties of the quantum Hall states with integer filling factors in graphene. The analysis is performed in the low-energy Dirac model in the meanfield approximation, in which the long-range Coulomb interaction is modified by the one-loop static screening effects in the presence of a background magnetic field. By utilizing a rather general ansatz for the propagator, in which all dynamical parameters are running functions of the Landau-level index n, we derive a self-consistent set of the Schwinger-Dyson (gap) equations and solve them numerically. The explicit solutions demonstrate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The temperature dependence of the energy gaps is also studied. The corresponding results mimic well the temperature dependence of the activation energies measured in experiment. It is also argued that, in principle, the Landau-level running of the quasiparticle dynamical parameters could be measured via optical studies of the integer quantum Hall states.

show abstract

Electrically Tunable Spin Exchange Splitting in Graphene Hybrid Heterostructure

Shin,

Kim,

Hong

et al. 2023

Adv Funct Materials

View full text Add to dashboard Cite

Graphene, with spin and valley degrees of freedom, fosters unexpected physical and chemical properties for the realization of next‐generation quantum devices. However, the spin‐symmetry of graphene is rather robustly protected, hampering manipulation of the spin degrees of freedom for the application of spintronic devices such as electric gate‐tunable spin filters. It is demonstrated that a hybrid heterostructure composed of graphene and LaCoO3 epitaxial thin film exhibits an electrically tunable spin‐exchange splitting. The large and adjustable spin‐exchange splitting of 155.9 – 306.5 meV is obtained by the characteristic shifts in both the spin‐symmetry‐broken quantum Hall states and the Shubnikov–de Haas oscillations. Strong hybridization‐induced charge transfer across the hybrid heterointerface has been identified for the observed spin exchange splitting. The substantial and facile controllability of the spin exchange splitting provides an opportunity for spintronics applications with the electrically‐tunable spin polarization in hybrid heterostructures.

show abstract

Spin and valley quantum Hall ferromagnetism in graphene

Abstract: 1 arXiv:1201.4167v1 [cond-mat.mes-hall]

Cited by 359 publications

References 52 publications

SO(5) symmetry in the quantum Hall effect in graphene

SO(5) symmetry in the quantum Hall effect in graphene

Generalized Landau level representation: Effect of static screening in the quantum Hall effect in graphene

Electrically Tunable Spin Exchange Splitting in Graphene Hybrid Heterostructure

Contact Info

Product

Resources

About