Details

Autor(en) / Beteiligte

• Kim, Youngwook
• Balram, Ajit C.
• Taniguchi, Takashi
• Watanabe, Kenji
• Jain, Jainendra K.
• Smet, Jurgen H.

Titel

Even denominator fractional quantum Hall states in higher Landau levels of graphene

Ist Teil von

• Nature physics, 2019-02, Vol.15 (2), p.154-158

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2019

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• An important development in the field of the fractional quantum Hall effect was the proposal that the 5/2 state observed in the Landau level with orbital index n  = 1 of two-dimensional electrons in a GaAs quantum well 1 originates from a chiral p -wave paired state of composite fermions that are topological bound states of electrons and quantized vortices. The excitations of this state, which is theoretically described by a ‘Pfaffian’ wavefunction 2 or its hole partner called the anti-Pfaffian 3 , 4 , are neither fermions nor bosons but Majorana quasiparticles obeying non-Abelian braid statistics 5 . This has inspired ideas for fault-tolerant topological quantum computation 6 and has also instigated a search for other states with exotic quasiparticles. Here we report experiments on monolayer graphene that show clear evidence for unexpected even denominator fractional quantum Hall physics in the n  = 3 Landau level. We numerically investigate the known candidate states for the even denominator fractional quantum Hall effect, including the Pfaffian, the particle–hole symmetric Pfaffian and the 221-parton states, and conclude that, among these, the 221-parton appears a potentially suitable candidate to describe the experimentally observed state. Like the Pfaffian, this state is believed to harbour quasi-particles with non-Abelian braid statistics 7 . New fractional quantum Hall states are observed in a higher Landau level in graphene. Calculations indicate that a non-Abelian parton state is the most likely candidate state, which has implications for topological quantum computation.