Phys. Rev. Lett. 89, 246804 (2002) [4 pages]NMR Investigation of How Free Composite Fermions Are at ν=1/2Received 15 May 2002; published 22 November 2002 NMR measurements of the electron spin polarization (P) have been performed on a 2D electron system at and around half-filled lowest Landau level. Comparing the magnetic field and the temperature dependence of P to models of free and interacting composite fermions (CF), the imbalance of spin-up and spin-down CF Fermi seas is mapped as a function of Zeeman energy. Independent measurements of the CF effective mass, g factor, and Fermi energy are obtained from the thermal activation of P in tilted fields. The filling factor dependence of the P for 2/5<ν<2/3 reveals a broken particle-hole symmetry for the partially polarized CF Fermi sea. © 2002 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.246804
DOI:
10.1103/PhysRevLett.89.246804
PACS:
73.43.–f, 71.10.Pm, 76.60.–k
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