Prof. John Wei bio

John Y.T. Wei Associate Professor Condensed Matter Physics
	60 St. George Street, Toronto, ON M5S1A7 Canada Phone: (416) 946-5943 Fax: (416) 978-2537 Office: MP 081 E-mail: wei at physics.utoronto.ca
Background Scholar, Canadian Institute for Advanced Research (since 1999) Member, Centre for Quantum Information and Quantum Control (since 2004) Member, Brockhouse Institute for Materials Research (since 2003) Postdoctoral Scholar & Research Fellow, California Institute of Technology (1996-99) Joint Research Student, IBM T. J. Watson Research Center (1992-95) M.S. & Ph.D., Columbia University (1991 & 1996) B.A., University of California Berkeley (1987) Research Go to Research Page *Interests: Nanoscale studies of exotic superconductivity, extreme magnetism & topological phenomena in oxides & intermetallics. Materials: Transition-metal oxides/chalcogenides, Fe-chalcogenides/pnictides, CeCoIn₅, Skutterudites, heavy-metal chalcogenides. Techniques: Cryomagnetic scanning tunneling microscopy (STM) & point-contact spectroscopy (PCS), pulsed laser deposition (PLD). My research is devoted to nanoscale study of unconventional superconducting and magnetic materials, as well as the emerging new class of topological materials. It is intended to examine the electronic properties of these materials at very short length scales, where the quantum ordering effects occur coherently without being averaged out over macroscopic distances, and manifest themselves as novel phenomena. It involves an unique combination of cryomagnetic, nanoprobe and nanofabrication techniques, with the application of both “top-down” and “bottom-up” approaches. Detailed understanding of these exotic electronic materials is of fundamental importance to condensed matter physics, and could also lend them to novel technological applications, ranging from superconducting to spintronic devices, as well as elements for quantum computation. Courses Taught* Physics 294H: Thermal Physics for Engineering Sciences Physics 335H: Quantum Mechanics for Electrical & Computer Engineering Physics 1850F: Foundations of Condensed Matter Physics Physics 326/327: 3rd/4th-Year Undergraduate Laboratory Physics 225H: 2nd-Year Undergraduate Laboratory Physics 281S: Introduction to Quantum Physics Select Publications 1. Lateral Imaging of the Superconducting Vortex Lattice using Doppler Modulated Scanning Tunneling Microscopy Applied Physics Letters 99, 192505 (2011). pdf 2. Andreev Nanoprobe of Half-Metallic CrO₂ Films using Superonducting Cuprate Tips Applied Physics Letters 99, 192508 (2011). pdf 3. Scanning tunneling spectroscopy study of c-axis proximity effect in epitaxial bilayer manganite/cuprate thin films, Physical Review B 84 104522 (2011). pdf 4. Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction Physical Review B 85 014503 (2012). pdf 5. STM Spectroscopy on Superconducting FeSe_1−xTe_x Single Crystals at 300 mK Journal of Physics and Chemistry of Solids, Volume 72-5, 483 (2011). pdf 6. Local tunneling probe of (110) Y_0.95Ca_0.05Ba₂Cu₃O_7-d thin films in a magnetic field Physical Review B 82, 054505 (2010). pdf 7. Andreev Spectroscopy Study of Multigap Pairing in PrOs₄Sb₁₂ Journal of the Physical Society of Japan 77, 21 (2008). pdf 8. Tunneling Spectroscopy on c-axis Y_1-xCa_xBa₂Cu₃O 7-d Thin Films Physical Review Letters 98, 177003 (2007). pdf 9. Conductance characteristics between a normal metal and a 2D Fulde-Ferrell-Larkin-Ovchnnikov superconductor: the Fulde-Ferrell state, Physical Review B 73, 214514 (2006). pdf 10. Suppression of low-energy Andreev states by a supercurrent in YBa2Cu3O7-d, Physical Review B 72, 054513 (2005). pdf 11. Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn5, Physical Review Letters 94, 107005 (2005). pdf Selective epitaxial growth of sub-micron complex oxide structures by amorphous SrTiO3, Applied Physics Letters 86, 192509 (2005). pdf Nuclear Spin Relaxation of ⁸Li in a Thin Film of La_0.67Ca_0.33MnO_3 R. I. Miller et al., preprint, to appear in Physica B (2006). Evidence for Current-Driven Phase Slips in YBa_2Cu_3O_7-d Microstrips P. Morales, M. DiCiano, and J. Y. T. Wei, preprint, to appear in AIP Conf. Proc. for LT24 (2006). Point Contact Spectroscopy Study of the Ferromagnetic Superconductor ZrZn_2 C. Turel, M. Tanatar, R. Hill, E. Yelland, S. Hayden, J. Y. T. Wei, preprint, to appear in AIP Conf. Proc. for LT24 (2006). Selective epitaxial growth of sub-micron complex oxide structures by amorphous SrTiO_3 P. Morales, M. DiCiano, and J. Y. T. Wei, Applied Physics Letters 86, 192509 (2005). Scanning tunneling spectroscopy under pulsed spin injection J. Ngai, et al., Applied Physics Letters 84, 1907 (2004). Nanoscale high-temperature superconductivity P. Mohanty, J. Y.T. Wei, V. Ananth, P. Morales, W. Skocpol, Physica C 408–410, 666 (2004). Spin-Injection Quasiparticle Nonequilibrium in Cuprate/Manganite Heterostructures, J. Y. T. Wei et al., Journal of Superconductivity 15-1, 67 (2002). Tunneling spectroscopy study of spin-polarized quasiparticle injection effects in cuprate/manganite heterostructures, J. Y. T. Wei et al., Journal of Applied Physics 85, 5350 (1999). Directional tunneling and Andreev reflection on YBa_2Cu_3O_{7-delta} single crystals: Predominance of d-wave pairing symmetry verified with the generalized BTK theory, J. Y. T. Wei et al., Physical Review Letters 81, 2542 (1998). Quasiparticle tunneling spectra of the high-Tc mercury cuprates: implication of the d-wave two-dimensional van Hove scenario, J. Y. T. Wei et al., Physical Review B 57, 3650 (1998). Back to Research Page
Physics Homepage	University of Toronto

Background

Scholar, Canadian Institute for Advanced Research (since 1999)
Member, Centre for Quantum Information and Quantum Control (since 2004)
Member, Brockhouse Institute for Materials Research (since 2003)
Postdoctoral Scholar & Research Fellow, California Institute of Technology (1996-99)
Joint Research Student, IBM T. J. Watson Research Center (1992-95)
M.S. & Ph.D., Columbia University (1991 & 1996)

Interests: Nanoscale studies of exotic superconductivity, extreme magnetism & topological phenomena in oxides & intermetallics.
Materials: Transition-metal oxides/chalcogenides, Fe-chalcogenides/pnictides, CeCoIn₅, Skutterudites, heavy-metal chalcogenides.
Techniques: Cryomagnetic scanning tunneling microscopy (STM) & point-contact spectroscopy (PCS), pulsed laser deposition (PLD).

My research is devoted to nanoscale study of unconventional superconducting and magnetic materials, as well as the emerging new class of topological materials. It is intended to examine the electronic properties of these materials at very short length scales, where the quantum ordering effects occur coherently without being averaged out over macroscopic distances, and manifest themselves as novel phenomena. It involves an unique combination of cryomagnetic, nanoprobe and nanofabrication techniques, with the application of both “top-down” and “bottom-up” approaches. Detailed understanding of these exotic electronic materials is of fundamental importance to condensed matter physics, and could also lend them to novel technological applications, ranging from superconducting to spintronic devices, as well as elements for quantum computation.

Physics 294H:        Thermal Physics for Engineering Sciences
Physics 335H:        Quantum Mechanics for Electrical & Computer Engineering
Physics 1850F:       Foundations of Condensed Matter Physics
Physics 326/327:    3rd/4th-Year Undergraduate Laboratory
Physics 225H:        2nd-Year Undergraduate Laboratory
Physics 281S:        Introduction to Quantum Physics

1. Lateral Imaging of the Superconducting Vortex Lattice using Doppler Modulated Scanning Tunneling Microscopy
Applied Physics Letters 99, 192505 (2011). pdf

2. Andreev Nanoprobe of Half-Metallic CrO₂ Films using Superonducting Cuprate Tips
Applied Physics Letters 99, 192508 (2011). pdf

3. Scanning tunneling spectroscopy study of c-axis proximity effect in epitaxial bilayer manganite/cuprate thin films,
Physical Review B 84 104522 (2011). pdf

4. Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction
Physical Review B 85 014503 (2012). pdf

5. STM Spectroscopy on Superconducting FeSe_1−xTe_x Single Crystals at 300 mK
Journal of Physics and Chemistry of Solids, Volume 72-5, 483 (2011). pdf

6. Local tunneling probe of (110) Y_0.95Ca_0.05Ba₂Cu₃O_7-d thin films in a magnetic field
Physical Review B 82, 054505 (2010). pdf

7. Andreev Spectroscopy Study of Multigap Pairing in PrOs₄Sb₁₂
Journal of the Physical Society of Japan 77, 21 (2008). pdf

8. Tunneling Spectroscopy on c-axis Y_1-xCa_xBa₂Cu₃O 7-d Thin Films
Physical Review Letters 98, 177003 (2007). pdf

9. Conductance characteristics between a normal metal and a 2D Fulde-Ferrell-Larkin-Ovchnnikov superconductor:
the Fulde-Ferrell state,
Physical Review B 73, 214514 (2006). pdf

10. Suppression of low-energy Andreev states by a supercurrent in YBa2Cu3O7-d,
Physical Review B 72, 054513 (2005). pdf

11. Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn5,
Physical Review Letters 94, 107005 (2005). pdf

Selective epitaxial growth of sub-micron complex oxide structures by amorphous SrTiO3,
Applied Physics Letters 86, 192509 (2005). pdf

Nuclear Spin Relaxation of ⁸Li in a Thin Film of La_0.67Ca_0.33MnO_3
R. I. Miller et al., preprint, to appear in Physica B (2006).

Evidence for Current-Driven Phase Slips in YBa_2Cu_3O_7-d Microstrips
P. Morales, M. DiCiano, and J. Y. T. Wei, preprint, to appear in AIP Conf. Proc. for LT24 (2006).

Point Contact Spectroscopy Study of the Ferromagnetic Superconductor ZrZn_2
C. Turel, M. Tanatar, R. Hill, E. Yelland, S. Hayden, J. Y. T. Wei, preprint, to appear in AIP Conf. Proc. for LT24 (2006).

Selective epitaxial growth of sub-micron complex oxide structures by amorphous SrTiO_3
P. Morales, M. DiCiano, and J. Y. T. Wei, Applied Physics Letters 86, 192509 (2005).

Scanning tunneling spectroscopy under pulsed spin injection
J. Ngai, et al., Applied Physics Letters 84, 1907 (2004).

Nanoscale high-temperature superconductivity
P. Mohanty, J. Y.T. Wei, V. Ananth, P. Morales, W. Skocpol, Physica C 408–410, 666 (2004).

Spin-Injection Quasiparticle Nonequilibrium in Cuprate/Manganite Heterostructures,
J. Y. T. Wei et al., Journal of Superconductivity 15-1, 67 (2002).

Tunneling spectroscopy study of spin-polarized quasiparticle injection effects in
cuprate/manganite heterostructures,
J. Y. T. Wei et al., Journal of Applied Physics 85, 5350 (1999).

Directional tunneling and Andreev reflection on YBa_2Cu_3O_{7-delta} single crystals:
Predominance of d-wave pairing symmetry verified with the generalized BTK theory,
J. Y. T. Wei et al., Physical Review Letters 81, 2542 (1998).

Quasiparticle tunneling spectra of the high-Tc mercury cuprates: implication of the
d-wave two-dimensional van Hove scenario,
J. Y. T. Wei et al., Physical Review B 57, 3650 (1998).

Back to Research Page