 
Summary: VOLUME 83, NUMBER 16 P H Y S I C A L R E V I E W L E T T E R S 18 OCTOBER 1999
Tunneling into Ferromagnetic Quantum Hall States: Observation of a Spin Bottleneck
H. B. Chan and R. C. Ashoori
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
L. N. Pfeiffer and K. W. West
Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974
(Received 26 May 1999)
We explore the characteristics of equilibrium tunneling of electrons from a 3D electrode into a
high mobility 2D electron system. For most noninteger filling factors, we find that tunneling can be
characterized by a single, welldefined tunneling rate. However, for spinpolarized quantum Hall states
(n 1, 3, and 1 3) tunneling occurs at two distinct rates that differ by up to 2 orders of magnitude.
The dependence of the two rates on temperature and tunnel barrier thickness suggests that slow inplane
spin relaxation creates a bottleneck for tunneling of electrons.
PACS numbers: 73.20.Dx, 71.45.Gm, 73.40.Gk
The interplay between Zeeman coupling of electronic
spins to an applied magnetic field and Coulomb interac
tions among electrons leads to remarkable spin configu
rations of quantum Hall systems. For instance, around
quantum Hall filling factor n 1, powerful exchange in
teractions align electron spins to form a nearly perfect
