2015/07/31 by Ajit C. Balram, Csaba Tőke, Arkadiusz Wójs +2
Materials Science · Physics and Astronomy · #Composite fermion #Condensed matter physics #Fermion #Fractional quantum Hall effect #Graphene #Graphene research and applications #Landau quantization #Magnetic field #Physics #Quantum Hall effect #Quantum and electron transport phenomena #Quantum mechanics #Quantum spin Hall effect #Spin (aerodynamics) #Topological Materials and Phenomena #Zeeman effect #Zeeman energy #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.92.205120
published as Phys. Rev. B 92, 205120 (2015) · 13 pages, 13 figures, published version
openalex publication_date 2015/11/19 · openalex created_date 2016/06/24 · arxiv created 2018/02/17 · arxiv updated 2018/02/20 · openalex updated_date 2026/08/05
Motivated by recent experiments that reveal expansive fractional quantum Hall states in the n=1 graphene Landau level and suggest a nontrivial role of the spin degree of freedom [F. Amet, A. J. Bestwick, J. R. Williams, L. Balicas, K. Watanabe, T. Taniguchi, and D. Goldhaber-Gordon, Nat. Commun. 6, 5838 (2015)], we perform an accurate quantitative study of the competition between fractional quantum Hall states with different spin polarizations in the n=1 graphene Landau level. We find that the fractional quantum Hall effect is well described in terms of composite fermions, but the spin physics is qualitatively different from that in the n=0 Landau level. In particular, for the states at filling factors \ensuremathν=s/(2s\ifmmode±\else\textpm\fi1), s positive integer, a combination of exact diagonalization and the composite fermion theory shows that the ground state is fully spin polarized and supports a robust spin-wave mode even in the limit of vanishing Zeeman coupling. Thus, even though composite fermions are formed, a mean-field description that treats them as weakly interacting particles breaks down, and the exchange interaction between them is strong enough to cause a qualitative change in the behavior by inducing full spin polarization. We also verify that the fully spin-polarized composite fermion Fermi sea has lower energy than the paired Pfaffian state at the relevant half fillings in the n=1 graphene Landau level, indicating an absence of composite fermion pairing at half filling in the n=1 graphene Landau level.