Quantum Hall Ferromagnets-III

1
Quantum Hall Ferromagnets-III
Les Houches June 2006
University of Texas at Austin
Ramin Abolfath Luis Brey Anton Burkov Rene
Cote Jim Eisenstein Herb Fertig Steve
Girvin Charles Hanna Tomas Jungwirth Kentaro
Nomura Leo Radzihovksy (Doug) Rajaraman
Mark Rasolt Jairo Sinova Kun Yang
2
Bilayer Excitonic Superfluidity
3
QHF Anisotropy
4
QHF Action (M1)
Burkov AHM PRB (2003)
Fluctuating 4-component Spinor
5
Bilayer Spin-Pseudospin Hamiltonian
Burkov AHM PRB (2003)
Exchange
Hartree
Small d
Large d
Jxx Jyy
6
N2 M1 (e.g. Bilayer) Anisotropy
Jungwirth AHM PRB 00
7
SU(2) Quantum Hall Ferromagnetism in GaAs
Eisenstein XY order
Shayegan Ising Order
8
Exciton BEC Basics
9
Excitons Elementary Excitations of Intrinsic
Semiconductors
Conduction Band
e
h
h
Valence Band
Snoke U. Pittsburgh Butov UCSD
10
Exciton Condensation is Spontaneous Interband
Coherence
n conduction band n valence band
Order Parameter
11
Excitonic BEC and Superfluidity?
12
Quantum Hall Superfluids
13
Electrons and Holes in the QH Regime
14
Josephson-like Currents
I N? e 2tsin(f) ??
Wen and Zee, Fogler and Wilczek, Balents and
Radzihovsky Stern et al., Fertig and Strayley, .
15
Bilayer Counterflow Transport
16
Electron-hole Pair Current
17
Exciton Superfluidity
Hall Angle Not Large
sxx ? 1000 e2/h
Kellogg and Eisenstein cond-mat/0401521
18
Spin Transfer
19
(No Transcript)
20
(No Transcript)
21
Spin Transfer Dynamics
Magnetic Anisotropy
Spin-Current Bias
External Magnetic Field
22
Bilayer PseudoSpin Transfer (Interlayer
Tunneling Theory)
23
Quantum Hall Bilayer Tunneling Anomaly is
Generalized Pseudospin Transfer Phenomena
24
Edge Pseudospin Transfer
Transport Orbitals
Condensate Orbitals
k X / l2
25
Pseudospin Ordered State Conductance
26
Pseudospin Transfer Theory
27
Current-Driven OrderParameter in
Antiferromagnets (Applied Quantum Hall
Ferromagnetism)
28
Current-Modulated Exchange Bias
Nunez et al. cond-mat/0510797 PRB (to appear)
Tsoi et al. cond-mat/0606 (submitted)
29
Quantum Hall Ferromagnets
Les Houches June 2006
University of Texas at Austin
Thanks for Listening!