B54.00007. Valley-resolved spin wave transport through graphene fractional quantum Hall states

Presented by: Haoxin Zhou


Abstract

High quality graphene heterostructures host an array of fractional quantum Hall isospin ferromagnets hosting diverse spin and valley orders. While a variety of phase transitions have been observed, disentangling the isospin phase diagram of these states is hampered by the absence of direct probes of spin and valley order. I will describe nonlocal transport measurements based on launching spin waves from a gate defined lateral heterojunction, performed in ultra-clean Corbino geometry graphene devices. At high magnetic fields, we find that the spin-wave transport signal is detected in all FQH states between ν = 0 and 1; however, between ν = 1 and 2 only odd numerator FQH states show finite nonlocal transport, despite the identical ground state spin polarizations in odd- and even numerator states. The results reveal that the neutral spin-waves are both spin and sublattice polarized making them a sensitive probe of ground state sublattice structure. Armed with this understanding, we use nonlocal transport signal to a magnetic field tuned isospin phase transition, showing that the emergent even denominator state at $\nu=\pm 1/2$ in monolayer graphene is indeed a multicomponent state featuring equal populations on each sublattice.

Authors

  • Haoxin Zhou
  • Hryhoriy Polshyn
  • Takashi Taniguchi
  • Kenji Watanabe
  • Andrea F. Young


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