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Quantum Hall Ferromagnets-III

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

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Quantum Hall Ferromagnets-III

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  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. |   |  Spontaneous Interlayer Phase Coherence = Excitonic Superfluidity = Pseudospin Ferromagnetism |0 = i (|  i+ei φ| i) Bilayer Excitonic Superfluidity

  3. QHF Anisotropy

  4. QHF Action (M=1) 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. S=N/2 state Uσ,σ Anisotropy N=2 M=1 (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. - e 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. Assemble Bilayer Add magnetic field Particle-hole transformation Electrons and Holes in the QH Regime

  14. Tunneling rate 0 0 Interlayer Voltage Josephson-like Currents I = NФe 2tsin(φ) ?? Wen and Zee, Fogler and Wilczek, Balents and Radzihovsky Stern et al., Fertig and Strayley, ….

  15. voltmeter I 0 0 voltmeter voltmeter I - e voltmeter Bilayer Counterflow Transport

  16. Electron-hole Pair Current

  17. Exciton Superfluidity Hall Angle Not Large σxx 1000 e2/h Kellogg and Eisenstein cond-mat/0401521

  18. Spin Transfer

  19. Spin-Transfer Theory Nunez+AHM cond-mat/0403710 Solid State Comm. ‘06

  20. Spin Transfer Dynamics Magnetic Anisotropy Spin-Current Bias External Magnetic Field

  21. Bilayer PseudoSpin Transfer (Interlayer Tunneling Theory)

  22. Quantum Hall Bilayer Tunneling Anomaly is Generalized Pseudospin Transfer Phenomena

  23. eV Edge Pseudospin Transfer Transport Orbitals Condensate Orbitals k = X / l2

  24. Pseudospin Ordered State Conductance

  25. Pseudospin Transfer Theory

  26. Current-Driven OrderParameter in Antiferromagnets (Applied Quantum Hall Ferromagnetism)

  27. Current-Modulated Exchange Bias Nunez et al. cond-mat/0510797 PRB (to appear) Tsoi et al. cond-mat/0606 (submitted)

  28. Quantum Hall Ferromagnets Les Houches June 2006 University of Texas at Austin Thanks for Listening!

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