Theory of nonequilibrium quantum matter and Spintronics

(718) 997-3379, SB B220
Ph.D., University of Toronto (2008)
Dr. Takei is currently not seeking any new students. 

Dr. Takei’s research focuses on understanding how macroscale, collective behavior of electrons and atoms in matter emerges from the laws of quantum mechanics governing their motion on the microscopic scale. His research activities primarily involve the use of analytical tools, supplemented by numerical techniques, to study the transport of mass, charge, spin, and/or heat through various low-dimensional quantum matter, including systems tuned close to thermal and quantum critical points, magnetically ordered systems (e.g., ferromagnets and antiferromagnets), as well as quantum spin systems hosting a myriad of interesting phenomena such as topological order and emergent excitations with fractional quantum numbers and statistics. Of particular interest is in understanding how spin angular momentum can be transported through insulating spin systems, an emerging subfield of condensed matter physics, still largely unexplored but a topic of relevance due to the recent exciting experimental developments that have come out of the field of spintronics.

Research in Dr. Takei’s group maintains a healthy synergy with experiments; they are a driving force for his theoretical efforts, and his goal, in turn, is to stimulate future experiments. Transport properties of different materials are theoretically studied with the machinery of linear-response theory, nonequilibrium quantum field theory, semi-classical dynamics, the renormalization group technique, scaling theories and more. While his ultimate goal is to advance the fundamental understanding of quantum matter via transport studies, an important subset of his work focuses on proposing novel device applications, such as new platforms for classical and quantum computation, based on the theoretical understanding that he develops through his research.

  1. S. Chakraborty and S. Takei, Controlling Orbital Magnetism of Band Electron Systems via Bath Engineering, arXiv:2401.09100.
  2. S. Takei and Y. Tserkovnyak, Detecting Fractionalization in Critical Spin Liquids using Color Centers, Phys. Rev. Research 6, 013043 (2024).
  3. J. Aftergood and S. Takei, Conductivity Enhancement in a Diffusive Fermi Liquid due to Bose-Einstein Condensation of Magnons, Phys. Rev. Lett. 130, 086702 (2023).
  4. D. A. Smith, S. Takei, B. Brann, L. Compton, F. Ramos-Diaz, M. Simmers, and S. Emori, Diffusive and Fluid- like Motion of Homochiral Domain Walls in Easy-Plane Magnetic Strips, Phys. Rev. Applied 16, 054002 (2021).
  5. M. Honari-Latifpour, J. Ding, S. Takei, M.-A. Miri, Self-organized vortex and antivortex patterns in laser arrays, Phys. Rev. Applied 16, 054010 (2021).
  6. A. Mishra, S. Takei, P. Simon, and M. Trif, Dynamical torques from Shiba states in s-wave superconductors, Phys. Rev. B 103, L121401 (2021).
  7. Y. Tserkovnyak, J. Zou, S. K. Kim, and S. Takei, Quantum hydrodynamics of spin winding, Phys. Rev. B 102, 224433 (2020).
  8. J. Aftergood and S. Takei, Probing quantum spin liquids in equilibrium via inverse spin Hall effect, Phys. Rev. Research 2, 033439 (2020).
  9. S. Takei, Spin transport in an electrically driven magnon gas near Bose-Einstein condensation: Hartree-Fock-Keldysh theory, Phys. Rev. B 100, 134440 (2019).
  10. J. Aftergood, M. Trif and S. Takei, Detecting spin transport in quantum magnets with photons, Phys. Rev. B 99, 174422 (2019).
  11. T. Taira, M. Ichioka, S. Takei, H. Adachi, Spin diffusion equation in superconductors in the vicinity of Tc, Phys. Rev. B 98, 214437 (2018).
  12. D. Joshi, A. P. Schnyder and S. Takei, Detecting end-states of a topological quantum paramagnet via spin Hall Noise spectroscopy, Phys. Rev. B 98, 064401 (2018).
  13. J. Aftergood and S. Takei, Noise in tunneling spin current across coupled quantum spin chains, Phys. Rev. B 97, 014427 (2018).
  14. S. Takei and M. Mohseni, Quantum control of topological defects in magnetic systems, Phys. Rev. B 97, 064401 (2018).
  15. S. Takei, Y. Tserkovnyak and M. Mohseni, Spin superfluid Josephson quantum devices, Phys. Rev. B 95, 144402 (2017).
  16. S. Takei, A. Yacoby, B. I. Halperin and Y. Tserkovnyak, Spin superflulidity through ν = 0 quantum Hall state of graphene, Phys. Rev. Lett. 116, 216801 (2016).
  17. S. K. Kim, S. Takei and Y. Tserkovnyak, Thermally activated phase slips in superfluid spin transport in magnetic wires, Phys. Rev. B 93, 020402(R) (2015).
  18. S. K. Kim, S. Takei and Y. Tserkovnyak, Topological spin transport by Brownian diffusion of domain walls, Phys. Rev. B 92, 220409(R) (2015).
  19. S. Takei and Y. Tserkovnyak, Nonlocal magnetoresistance mediated by spin superfluidity, Phys. Rev. Lett. 115, 156604 (2015).
  20. S. Takei, T. Moriyama, T. Ono and Y. Tserkovnyak, Antiferromagnet-mediated spin transfer between a metal and a ferromagnet, Phys. Rev. B 92, 020409(R) (2015).
  21. T. Moriyama, S. Takei, M. Nagata, Y. Yoshimura, N. Matsuzaki, T. Terashima, Y. Tserkovnyak, T. Ono, Anti-damping spin transfer torque through epitaxial Nickel oxide, Appl. Phys. Lett. 106, 162406 (2015).
  22. S. Takei, B. Rosenow, and A. Stern, Noise due to neutral modes in the ν=2/3 fractional quantum Hall state, Phys. Rev. B 91, 241104(R) (2015).
  23. S. Takei, B. I. Halperin, A. Yacoby and Y. Tserkovnyak, Superflulid spin transport through antiferromagnetic insulators, Phys. Rev. B 90, 094408 (2014).
  24. Y. Fan, P. Upadhyaya, X. Kou, M. Lang, S. Takei, Z. Wang, J. Tang, L. He, L.-T. Chang, M. Montazeri, G. Yu, W. Jiang, T. Nie, R. N. Schwartz, Y. Tserkovnyak, and K. L. Wang, Magnetization switching via giant spin-orbit torque in a magnetically doped topological insulator heterostructure, Nature Mater. 13, 699 (2014).
  25. G. Yu, P. Upadhyaya, Y. Fan, J. G Alzate, W. Jiang, K. L. Wong, S. Takei, S. A. Bender, M. Lang, J. Tang, Y. Tserkovnyak, P. Khalili Amiri and K. L. Wang, Switching of perpendicular magnetization by spin-orbit torque in the absence of external magnetic fields, Nature Nano. 9, 548 (2014).
  26. S. Takei and Y. Tserkovnyak, Superflulid spin transport through easy-plane ferromagnetic insulators, Phys. Rev. Lett. 112, 227201 (2014).
  27. G. R. Boyd, S. Takei, and V. Galitski, Nonequilibrium probe of paired electron pockets in the underdoped cuprates, Solid State Comm. 189, 63 (2014).
  28. S. Takei, B. M. Fregoso, H.-Y. Hui, A. M. Lobos, and S. Das Sarma, The soft superconducting gap in semiconductor Majorana nanowires, Phys. Rev. Lett. 110, 186803 (2013).
  29. S. Takei, B. M. Fregoso, V. Galitski and S. Das Sarma, Topological superconductivity and Majorana fermions in hybrid structures involving cuprate high-Tc superconductors, Phys. Rev. B 87, 014504 (2013).
  30. S. Takei and V. Galitski, Microscopic theory for a ferromagnetic-nanowire superconductor heterostructure: Transport, fluctuations and topological superconductivity, Phys. Rev. B, 86, 054521 (2012).
  31. S. Takei, V. M. Galitski, and K. D. Osborn, Squeezed noise due to two-level systems in superconducting resonator circuits, Phys. Rev. B 85, 104507 (2012).
  32. S. Takei, C.-H. Lin, B. M. Anderson, V. Galitski, Low-density molecular gas of tightly-bound Rashba-Dresselhaus fermions, Phys. Rev. A 85, 023626 (2012).
  33. S. Takei and B. Rosenow, Neutral mode heat transport and fractional quantum Hall shot noise, Phys. Rev. B 84, 235316 (2011).
  34. B. Obert, S. Takei, and W. Metzner, Anomalous criticality near semimetal-to-superfluid quantum phase transition in a two-dimensional Dirac cone model, Ann. Phys. (Berlin) 523, 621 (2011).
  35. S. Takei, M. Milletari, and B. Rosenow, Nonequilibrium electron spectroscopy of Luttinger liquids, Phys. Rev. B 82, 041306(R) (2010).
  36. S. Takei, W. Witczak-Krempa, and Y. B. Kim, Nonequilibrium quantum criticality in bilayer itinerant ferromagnets, Phys. Rev. B 81, 125430 (2010).
  37. P. Strack, S. Takei, and W. Metzner, Anomalous scaling of fermions and order parameter fluctuations at quantum criticality, Phys. Rev. B 81, 125103 (2010).
  38. S. Takei and Y. B. Kim, Nonequilibrium-induced metal-superconductor quantum phase transition in graphene, Phys. Rev. B, 78, 165401 (2008).
  39. S. Takei and Y. B. Kim, Theory of electron-phonon interaction in a nonequilibrium open electronic system, Phys. Rev. B, 76, 115304 (2007).
  40. A. Mitra, S. Takei, Y. B. Kim, and A. J. Millis, Quantum criticality in open electronic systems, Phys. Rev. Lett., 97, 236808 (2006).
  41. S. Takei, Y. B. Kim, and A. Mitra, Enhanced Fano factor in a molecular transistor coupled to phonons, Phys. Rev. B, 72, 075337 (2005).
  42. S. Takei, C.-H. Chung, and Y. B. Kim, Evolution of the single-hole spectral function across a quantum phase transition in the anisotropic-triangular-lattice antiferromagnet, Phys. Rev. B, 70, 104402 (2004).