Beyond the Three Traditional Assumptions of Spintronics
Spintronics has transformed our ability to generate, transfer, and manipulate angular momentum in solids, enabling powerful strategies for current-driven control of magnetic states and devices. Despite its remarkable success, the field has traditionally been built upon three simplifying assumptions: a classical description of localized spins (magnetic moments), exchange interactions that act purely between spin degrees of freedom, and the predominance of spin dipole moments as the primary carriers of angular momentum. This talk explores what new physics emerges when these assumptions are relaxed and when additional internal degrees of freedom are taken seriously.
In particular, I will discuss the role of longitudinal quantum fluctuations in spin transfer processes [1], revealing regimes where angular momentum transport cannot be captured by conventional transverse spin dynamics. I will then introduce current-driven control of magnetism mediated by orbital exchange interactions [2], highlighting how orbital degrees of freedom provide a qualitatively new channel for coupling electric currents to magnetic order. Finally, I will present multipolar pathways for angular-momentum transport that go beyond conventional dipolar mechanisms [3], opening a broader framework for spintronics and orbitronics in which higher-rank moments play an active and controllable role.
[1] T. Lee et al., “Signatures of longitudinal spin pumping in a magnetic phase transition,” Nature, vol. 638, pp. 106–111, Jan. 2025, doi: 10.1038/s41586-024-08367-z.
[2] G.-H. Lee, K.-W. Kim, and K.-J. Lee, “Orbital exchange-mediated current control of magnetism,” unpublished, 2025.
[3] H.-W. Ko and K.-J. Lee, “Magnetic octupole Hall effect in d-wave altermagnets,” unpublished, Aug. 2025, arXiv:2508.00794.
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Kyung-Jin Lee of KAIST/Korea
Beyond the Three Traditional Assumptions of Spintronics
Spintronics has transformed our ability to generate, transfer, and manipulate angular momentum in solids, enabling powerful strategies for current-driven control of magnetic states and devices. Despite its remarkable success, the field has traditionally been built upon three simplifying assumptions: a classical description of localized spins (magnetic moments), exchange interactions that act purely between spin degrees of freedom, and the predominance of spin dipole moments as the primary carriers of angular momentum. This talk explores what new physics emerges when these assumptions are relaxed and when additional internal degrees of freedom are taken seriously.
In particular, I will discuss the role of longitudinal quantum fluctuations in spin transfer processes [1], revealing regimes where angular momentum transport cannot be captured by conventional transverse spin dynamics. I will then introduce current-driven control of magnetism mediated by orbital exchange interactions [2], highlighting how orbital degrees of freedom provide a qualitatively new channel for coupling electric currents to magnetic order. Finally, I will present multipolar pathways for angular-momentum transport that go beyond conventional dipolar mechanisms [3], opening a broader framework for spintronics and orbitronics in which higher-rank moments play an active and controllable role.
[1] T. Lee et al., “Signatures of longitudinal spin pumping in a magnetic phase transition,” Nature, vol. 638, pp. 106–111, Jan. 2025, doi: 10.1038/s41586-024-08367-z.
[2] G.-H. Lee, K.-W. Kim, and K.-J. Lee, “Orbital exchange-mediated current control of magnetism,” unpublished, 2025.
[3] H.-W. Ko and K.-J. Lee, “Magnetic octupole Hall effect in d-wave altermagnets,” unpublished, Aug. 2025, arXiv:2508.00794.
Biography:
Kyung-Jin Lee (M ’08, SM ’23) received the B.S., M.S., and Ph.D. degrees from Korea Advanced Institute of Science and Technology (KAIST) in 1994, 1996, and 2000. He was a postdoctoral fellow at SPINTEC in Grenoble, France, from 2003 to 2005. He worked at Samsung Advanced Institute of Technology for five years and at Korea University for 15 years. In October 2020, he joined the Department of Physics at KAIST, where he is currently a KAIST Endowed Chair Professor. Dr. Lee is the recipient of several awards including the Order of Science and Technology Merit Medal from the Korean government and “100 Future Technologies and Leading Scientists in Korea: Spin Memory and Logic Devices” from the National Academy of Engineering of Korea. He is a Fellow of the American Physical Society. His current research interests include angular momentum dynamics and quantum spin transfer.
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Kyung-Jin Lee
Beyond the Three Traditional Assumptions of Spintronics
Spintronics has transformed our ability to generate, transfer, and manipulate angular momentum in solids, enabling powerful strategies for current-driven control of magnetic states and devices. Despite its remarkable success, the field has traditionally been built upon three simplifying assumptions: a classical description of localized spins (magnetic moments), exchange interactions that act purely between spin degrees of freedom, and the predominance of spin dipole moments as the primary carriers of angular momentum. This talk explores what new physics emerges when these assumptions are relaxed and when additional internal degrees of freedom are taken seriously.
In particular, I will discuss the role of longitudinal quantum fluctuations in spin transfer processes [1], revealing regimes where angular momentum transport cannot be captured by conventional transverse spin dynamics. I will then introduce current-driven control of magnetism mediated by orbital exchange interactions [2], highlighting how orbital degrees of freedom provide a qualitatively new channel for coupling electric currents to magnetic order. Finally, I will present multipolar pathways for angular-momentum transport that go beyond conventional dipolar mechanisms [3], opening a broader framework for spintronics and orbitronics in which higher-rank moments play an active and controllable role.
[1] T. Lee et al., “Signatures of longitudinal spin pumping in a magnetic phase transition,” Nature, vol. 638, pp. 106–111, Jan. 2025, doi: 10.1038/s41586-024-08367-z.
[2] G.-H. Lee, K.-W. Kim, and K.-J. Lee, “Orbital exchange-mediated current control of magnetism,” unpublished, 2025.
[3] H.-W. Ko and K.-J. Lee, “Magnetic octupole Hall effect in d-wave altermagnets,” unpublished, Aug. 2025, arXiv:2508.00794.
Biography:
Kyung-Jin Lee (M ’08, SM ’23) received the B.S., M.S., and Ph.D. degrees from Korea Advanced Institute of Science and Technology (KAIST) in 1994, 1996, and 2000. He was a postdoctoral fellow at SPINTEC in Grenoble, France, from 2003 to 2005. He worked at Samsung Advanced Institute of Technology for five years and at Korea University for 15 years. In October 2020, he joined the Department of Physics at KAIST, where he is currently a KAIST Endowed Chair Professor. Dr. Lee is the recipient of several awards including the Order of Science and Technology Merit Medal from the Korean government and “100 Future Technologies and Leading Scientists in Korea: Spin Memory and Logic Devices” from the National Academy of Engineering of Korea. He is a Fellow of the American Physical Society. His current research interests include angular momentum dynamics and quantum spin transfer.
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