Sajeev John

Theoretical Condensed Matter Physics and Quantum Optics

Professor: Ph.D., Harvard (1984); Assistant Professor, Princeton (1986-89); S.B. M.I.T., (1979); NSERC Postdoctoral Fellow, University of Pennsylvania (1984-86); Consultant, Exxon Research (1985-89); Consultant, Bell Communication Research (1989); Principal Investigator,  Photonics Research Ontario; Herzberg Medal (1995), McLean Senior Fellow (1996), Steacie Prize (1997), Killam Fellowship (1998-2000).

Condensed matter physics, disordered systems, optical properties, localization, many-body theory, magnetism, superconductivity.

Phone: (416) 978-3459     Fax: (416) 978-2537 e-mail: john@physics.utoronto.ca

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Research Interests

Photon Localization and Photonic Bandgaps

It has recently been demonstrated experimentally that in a new class of dielectrics light can exhibit localization. We are studying the implications of localization in quantum-electrodynamics. This involves new phenomena such as photon-atom bound states as well as the reexamination of nonlinear optics, cooperative behaviour of atoms, laser activity and photo-chemistry in this context. These dielectric materials are the photonic analogs of semi-conductors and may have important technological applications.

High Temperature Superconductivity

High Tc transition metal oxides constitute a major new frontier in solid state theory in which electron-electron interactions are not small compared to band effects.  Novel collective effects in the electron spin field  interact strongly with the electronic charge giving rise to what is known as a quantum spin liquid phase. We are investigating the nature of this new magnetic phase and possible origins of superconductive pairing.

Multiple Light Scattering Spectroscopy

In disordered media, multiple scattering of light leads to complication for spectroscopic studies. Recently, we have developed a theory that enables the reconstruction of the dynamic structure factor of the medium from a light scattering experiment. A major application is the use of photon diffusion as a diagnostic tool for metabolic imaging in medicine. We are currently trying to refine this spectroscopic tool to detect tumors in biological tissue. Another important application is in the understanding of the newly discovered ''Laser Paints''

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Current Research Program

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Current Members of the Research Group

     Ph.D. Students

Research Associates and PDF's

     Visiting Professor

  • Valery Rupasov
* McLean Junior Fellow

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Selected Publications

  1. "Electromagnetic Absorption in a Disordered Medium near a Photon Mobility Edge", Sajeev John, Phys. Rev. Lett. 53, 2169 (1984).
  2. "Spin Glass State of a Randomly diluted Granular Superconductor", Sajeev John and T.C. Lubensky, Phys. Rev. Lett. 55, 1014 (1985). ABSTRACTPDF
  3. "Theory of the Electron Band Tails and the Urbach Optical Absorption Edge", Sajeev John, C. Soukoulis, Morrel H. Cohen and E.N. Economou, Phys. Rev. Lett. 57, 1777 (1986).   ABSTRACTPDF
  4. "Strong Localization of Photons in Certain Disordered Dielectric Superlattices", Sajeev John, Phys. Rev. Lett. 58, 2486 (1987).  ABSTRACTPDF
  5. "Localization and the Density of States for an Electron in a Quantized Elastic Continuum", Sajeev John, Physical Review B 35, 9291 (1987).   ABSTRACTPDF
  6. "Density of States for an Electron in a Correlated Gaussian Random Potential: Theory of the Urbach Tail", Sajeev John, M.Y. Chou, M.H. Cohen and C.M. Soukoulis, Phys. Rev. B 37, 6963 (1988).   ABSTRACTPDF
  7. "Temperature Dependence of the Urbach Edge: A Theory of Multiple Phonon Absorption and Emission Sidebands", C. Grein and Sajeev John, Phys. Rev. B 39, 1140 (1989).   ABSTRACTPDF
  8. ''Localization of Light'', S. John, Physics Today, May (1991), Cover Story.
  9. ''Quantum Electrodynamics Near a Photonic Band Gap: Photons Bound States and Dressed Atoms'', S. John and J. Wang, Phys. Rev. Lett. 64, 2418 (1990).  ABSTRACTPDF
  10. ''Nonlinear Optical Solitary Waves in a Photonic Bandgap'', S. John and N. Akozbek, Physical Review Letters 71, 1168 (1993). ABSTRACTPDF
  11. ''Topological Magnetic Solitons in the Two-Dimensional Mott-Hubbard Gap'', S. John and A. Golubentsev, Physical Review Letters 71, 3343 (1993).  ABSTRACTPDF
  12. "Spontaneous Emission near the Edge of a Photonic Bandgap", Sajeev John and Tran Quang, Physical Review A 50 1764 (1994).  ABSTRACTPDF
  13. "Spin-flux and Magnetic Solitons in an Interacting Two-Dimensional Electron Gas: Topology of Two-Valued Wavefunctions", Sajeev John and A. Golubentsev, Physical Review B51, 381 (1995).   ABSTRACTPDF
  14. ''Localization of Superradiance near a Photonic Bandgap'', S. John and T. Quang, Phys. Rev. Lett. 74, 3419 (1995).   ABSTRACTPDF
  15. ''Optical Coherence Propagation and Imaging in a Multiple Scattering Medium'', S. John, G. Pang and Y. Yang, Journal of Biomedical Optics 1, number 2, 180 (1996).  ABSTRACT
  16. ''Quantum Optical Spin-Glass State of Impurity Two-Level Atoms in a Photonic Bandgap'', S. John and T. Quang, Phys. Rev. Lett. 76, 1320 (1996).   ABSTRACTPDF
  17. ''Resonant Nonlinear Dielectric Response in a Photonic Band Gap Material'', S. John and T. Quang, Phys. Rev. Lett. 76, 2484 (1996). ABSTRACTPDF
  18. ''Theory of Lasing in a Multiple Scattering Medium'', S. John and G. Pang, Physical Review A 54, 3642 (1996).  ABSTRACTPDF
  19. "Collective Switching and Inversion without Fluctuation of Two-Level Atoms in Confined Photonic Systems", Sajeev John and Tran Quang, Physical Review Letters 78, 1888 (1997).  ABSTRACTPDF POSTSCRIPT
  20. "Multi-photon Localization and Propagating Quantum Gap Solitons in a Frequency Gap Medium", Sajeev John and Valery Rupasov, Physical Review Letters 79, 821 (1997).    ABSTRACTPDF POSTSCRIPT
  21. "Coherent Control of Spontaneous Emission Near a Photonic Band Edge: A Single-Atom Optical Memory Device", Tran Quang, M. Woldeyohannes, Sajeev John and G.S. Agarwal, Physical Review Letters 79 5238 (1997). ABSTRACTPDF POSTSCRIPT
  22. "Frozen Light", Sajeev John, Nature 390, 661 (1997). ABSTRACT
  23. "Charged Bosons in a Doped Mott Insulator: Electronic Properties of Domain Wall Solitons and Meron-Vortices", Mona Berciu and Sajeev John, Physical Review B 57 9521 (1998).   ABSTRACTPDF POSTSCRIPT
  24. "Midgap States of a Two-Dimensional Antiferromagnetic Mott Insulator: Electronic Structure of Meron-Vortices", Sajeev John, Mona Berciu and A. Golubentsev, Europhysics Letters 41 (1), 31 (1998). ABSTRACTPDF
  25. "Photonic Band Gap Formation in Certain Self-Organizing Systems", Kurt Busch and Sajeev John, Physical Review E 58, 3896 (1998). ABSTRACTPDF POSTSCRIPT
  26. "Liquid Crystal Photonic Band Gap Materials: The Tunable Electromagnetic Vacuum", Kurt Busch and Sajeev John, Physical Review Letters 83 (5), 967-970 (1999).ABSTRACTPDF  POSTSCRIPT
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