Metamorphosis of a Quantum Hall Bilayer State into a Composite Fermion Metal

TL;DR

This paper investigates how quantum Hall bilayer states transition into composite fermion metals when the tunneling gap collapses, revealing this transformation through inelastic light scattering measurements of spin excitations.

Contribution

It provides experimental evidence of the quantum Hall bilayer to composite fermion metal transition via inelastic light scattering, highlighting the role of spin excitations.

Findings

Observation of continua of spin excitations below the spin-wave mode

Identification of quasiparticle excitations with spin and Landau level changes

Evidence of the collapse of the tunneling gap leading to a composite fermion metal state

Abstract

Composite fermion metal states emerge in quantum Hall bilayers at total Landau level filling factor $\nu_T$=1 when the tunneling gap collapses by application of in-plane components of the external magnetic field. Evidence of this transformation is found in the continua of spin excitations observed by inelastic light scattering below the spin-wave mode at the Zeeman energy. The low-lying spin modes are interpreted as quasiparticle excitations with simultaneous changes in spin orientation and composite fermion Landau level index.