Topological Systems and Spin-Orbit Coupling

Phase transitions in condensed matter physics generally have been identified with an order parameter that spontaneously breaks the symmetry of the system and develops long range order, such as for the magnetization that develops in a ferromagnet below the Curie temperature or the staggered magnetization below the Néel temperature in an antiferromagnet.  With the discovery of the Integer Quantum Hall Effect, and now for Topological Insulators (TI), the traditional classification of quantum phases of matter has expanded.  These latter systems lack the concept of spontaneous symmetry breaking, rather exhibiting topological order associated with the presence of nontrivial topological components that lead to gapless boundary modes with chirality. One of the essential properties of TI's is a strong spin-orbit interaction, which interaction becomes larger the heavier the element.  For the well-studied 3d systems the spin-order interaction typically does not play an essential role, which is one of the reasons attention in the condensed matter community has turned to 4d, 5d, and 5f systems. 

Further expansion of these new and fascinating systems now includes Topological Semimetals.  In the Weyl semimetal CeAlGe, Joe Checkelsky's group at M.I.T. has discovered the particularly interesting phenomenon of Singular Angular MagnetoResistance (SAMR).  For a general explanation please see the news item at https://news.mit.edu/2019/approaching-magnetic-singularity-0620, while the publication can be found at  Science 365, 377 (2019);  (perspective by Hassinger and Meng).

Half-Heusler, Kagome Topological Systems and Related

In the so-called Z₂ two-dimensional and three-dimensional systems, these topologically protected metallic states are of interest not only from a fundamental point of view, but also because they have the technological potential to transform spintronics and quantum computation applications. Even more interesting are systems that exhibit both symmetry breaking order parameters and topologically nontrivial states, which can give rise to exotic collective modes and states.  One such family is represented by the cubic half-Heusler materials where the antiferromagnetism breaks time reversal and translational symmetries but preserves the combination, leading to a new type of system, the antiferromagnetic topological insulator.  Materials where the magnetic ions occupy a kagome lattice provide another class of very interesting systems.  

Magnetism and Fermiology of Kagome Magnet YMn₆Sn₄Ge₂, Hari Bhandari, Rebecca L. Dally, Peter E. Siegfried, Resham Regmi, Kirrily C. Rule, Songxue Chi, Jeffrey W. Lynn, I. I. Mazin, and Nirmal J. Ghimire, Nature Partner Journal: Quantum Materials 9:6 (2024)

Anomalous Hall effect Emerging from Field-induced Weyl nodes in SmAlSi, Yuxiang Gao, Shiming Lei, Eleanor M. Clements, Yichen Zhang, Xue-Jian Gao, Songxue Chi,Kam Tuen Law, Ming Yi, Jeffrey W. Lynn,and Emilia Morosan, (submitted).

Formation of a simple cubic antiferromagnet through charge ordering in a double Dirac material, Tanya. Berry, Vincent C. Morano, Thomas Halloran, X. Zhang, T. J. Slade, A. Sapkota, S. L. Bud’ko, W. Xie, D. H. Ryan, Z. Xu, Y. Zhao, Jeffrey W. Lynn, T. Fennell, P.C. Canfield, Collin L. Broholm, and Tyrel M. McQueen, (submitted).

Noncollinear 2k antiferromagnetism in the Zintl semiconductor Eu₅In₂Sb₆, Vincent C. Morano, Jonathan Gaudet, Nicodemos Varnava, Tanya Berry, Thomas Halloran, Chris J. Lygouras, Xiaoping Wang, Christina M. Hoffman, Guangyong Xu, Jeffrey W. Lynn, Tyrel McQueen, David Vanderbilt, and Collin L. Broholm, Phys. Rev. B 109, 014432 (2024).

Orbital Character of the Spin-reorientation Transition in TbMn₆Sn₆, S. X. M. Riberolles, Tyler J. Slade, R. L. Dally, P. M. Sarte, Bing Li, Tianxiong Han, H. Lane, C. Stock, H. Bhandari, N. J. Ghimire, D. L. Abernathy, P. C. Canfield, J. W. Lynn, B. G. Ueland, and R. J. McQueeney, Nature Communications s41467-023-38174-5 (2023).

Electronic Commensuration of a Spin Moiré Superlattice in a Natural Magnetic Heterostructure, Takashi Kurumaji, Nisarga Paul, Shiang Fang, Paul M. Neves, Mingu Kang, Jonathan S. White, Taro Nakajima, David Graf, Linda Ye, Mun K. Chan, Takehito Suzuki, Jonathan Denlinger, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Yang Zhao, Jeffrey W. Lynn, Efthimios Kaxiras, Riccardo Comin, Liang Fu, and Joseph G. Checkelsky (submitted).

Incommensurate magnetic orders and topological Hall effect in the square-net centrosymmetric EuGa₂Al₂ system, Jaime M. Moya, Shiming Lei, Eleanor M. Clements, Caitlin S. Kengle, Stella Sun, Kevin Allen, Qizhi Li, Y. Y. Peng, Ali A. Husain, Matteo Mitrano, Matthew J. Krogstad, Raymond Osborn, Anand B. Puthirath, Songxue Chi, L. Debeer-Schmitt, J. Gaudet, P. Abbamonte, Jeffrey W. Lynn, and E. Morosan, Phys. Rev. Materials 6, 074201 (2022).

Magnetization-driven Lifshitz transition and charge-spin coupling in the kagome metal YMn₆Sn₆, Peter E. Siegfried, Hari Bhandari, David C. Jones, Madhav P. Ghimire, Rebecca L. Dally, Lekh Poudel, Markus Bleuel, Jeffrey W. Lynn, Igor I. Mazin, and Nirmal J. Ghimire, Communications Physics (2022).

Isotropic Nature of the Metallic Kagome Ferromagnet Fe₃Sn₂ at High Temperatures, Rebecca L. Dally, Daniel Phelan, Nicholas Bishop, Nirmal J. Ghimire and Jeffrey W. Lynn, Crystals 11, 307 (2021).

Field-tuned Magnetic Structure and Phase Diagram of the Honeycomb Magnet YbCl₃, Yiqing Hao, HongLiang Wo, YiMeng Gu, XiaoWen Zhang, YiQing Gu, ShiYi Zheng, Yang Zhao, GuangYong Xu, Jeffrey W. Lynn, Kenji Nakajima, Naoki Murai, WenBin Wang, and Jun Zhao, Science China Physics, Mechanics & Astronomy 64, 237411 (2021).

Chiral properties of the zero-field spiral state and field-induced magnetic phases of the itinerant kagome metal YMn₆Sn₆, Rebecca L. Dally, Jeffrey W. Lynn, Nirmal J. Ghimire, Dina Michel, Peter Siegfried, and Igor I. Mazin, Phys. Rev. B 103, 094413 (2021).

Competing Magnetic Phases and Fluctuation-driven Scalar Spin Chirality in the Kagome Metal YMn₆Sn₆, Nirmal J. Ghimire, Rebecca L. Dally, L. Poudel, D. C. Jones, D. Michel, N. Thapa Magar, M. Bleuel, Michael A. McGuire, J. S. Jiang, John F. Mitchell, Jeffrey W. Lynn, and I. I. Mazin, Science Advances 6, eabe2680 (2020).  Press Release.

Correlating Magnetic Structure and Magnetotransport in Semimetal Thin Films of Eu_1-xSm_xTiO₃, Zach Porter, Ryan F. Need, Kaveh Ahadi, Yang Zhao, Zhijun Xu, Brian J. Kirby, Jeffrey W. Lynn, Susanne Stemmer, and Stephen D. Wilson, Phys. Rev. Materials 4, 054411 (2020).

Magnetic Phase Transitions and Spin Density Distribution in the Molecular Multiferroic System GaV₄S₈, Rebecca L. Dally, William D. Ratcliff II, Lunyong Zhang, Heung-Sik Kim, Markus Bleuel, J. W. Kim, Kristjan Haule, David Vanderbilt, Sang-Wook Cheong, and Jeffrey W. Lynn, Phys. Rev. B102, 014410 (2020).

Singular Angular Magnetoresistance and Spontaneous Symmetry Breaking in a Magnetic Nodal Semimetal, T. Suzuki, L. Savary, J.-P. Liu, J. W. Lynn, L. Balents, and J. G. Checkelsky, Science (2019).  Press Release.

Carrier Density Control of Magnetism and Berry Phases in Doped EuTiO₃, Kaveh Ahadi, Zhigang Gui, Zach Porter, Jeffrey W. Lynn, Zhijun Xu, Stephen D. Wilson, Anderson Janotti, and Susanne Stemmer,, APL Materials 6, 056105 (2018).

Amplitude Mode in a Classical, Two-dimensional Triangular Antiferromagnet, Rebecca L. Dally, Yang Zhao, Zhijun Xu, Robin Chisnell,  Matthew Stone, Jeffrey W. Lynn, Leon Balents, and Stephen D. Wilson, Nature Communications 9, 2188 (2018).

Topological RPdBi half-Heusler semimetals:  a new family of non-centrosymmetric magnetic superconductors, Y. Nakajima, R. Hu, K. Kirshenbaum, A. Hughes, P. Syers, X. Wang, K. Wang, R. Wang, S. Saha, D. Pratt, J.W. Lynn, and J. Paglione, Science Advances 1, e1500242 (2015).

Large Anomalous Hall Effect in a Half Heusler Antiferromagnet, T. Suzuki, R. Chisnell, A. Devarakonda, Y.-T. Liu, J. W. Lynn, and J. G. Checkelsky, Nature Physics 12, 1119 (2016).  Press Release.

5d sytems;  Iridates

Topological Singularity-Induced Kohn Anomaly in a Weyl Semimetal, Thanh Nguyen, Fei Han, Nina Andrejevic, Ricardo Pablo-Pedro, Anuj Apte, Yoichiro Tsurimaki, Zhiwei Ding, Kunyan Zhang, Ahmet Alatas, Ercan Alp, Songxue Chi, Jaime Fernandez-Baca, Masaaki Matsuda, David A. Tennant, Yang Zhao, Zhijun Xu, Jeffrey W. Lynn, Shengxi Huang, and Mingda Li, Phys. Rev. Lett. 124, 236401 (2020).

Influence of Electron-doping on the Ground State of (Sr_1-xLa_x)₂IrO₄, Xiang Chen, Tom Hogan, D. Walkup, Wenwen Zhou, M. Pokharel, Mengliang Yao, Wei Tian, Thomas Z. Ward, Y. Zhao, D. Parshall, C. Opeil, J. W. Lynn, Vidya Madhavan, and Stephen D. Wilson, Phys. Rev. B 92, 017125 (2015).

Carrier Localization and Electronic Phase Separation in a doped Spin-Orbit Driven Mott Phase in Sr₃(Ir_1-xRu_x)₂O₇, Chetan Dhital, Tom Hogan, Wenwen Zhou, Xiang Chen, Zhensong Ren, Mani Pokharel, Yoshinori Okada, M. Heine, Wei Tian, Z. Yamani, C. Opeil, J. S. Helton, J. W. Lynn, Ziqiang Wang, Vidya Madhavan, and Stephen D. Wilson, Nature Communications 5, 3377 (2014).

Cd-doping effects in Ce₂MIn₈ (M=Rh and Ir) Heavy Fermion Compounds, C. Adriano, C. Giles, E. M. Bitter, L. N. Coelho, F. de Bergevin, C. Mazzoll, L. Paolasini, W. Ratcliff, R. Bindel, J. W. Lynn, Z. Fisk, and P. G. Pagliuso, Phys. Rev. B 81, 245115 (2010).

Novel Coexistence of Superconductivity with Two Distinct Magnetic Orders in Heavy Fermion Ce(Rh,Ir)In₅, A. D. Christianson, A. Llobet, W. Bao, J. S. Gardner, I. P. Swainson, J. W. Lynn, J.-M. Mignot, K. Prokes, P. G. Pagliuso, N. O. Moreno, J. L. Sarrao, and A. H. Lacerda, Phys. Rev. Lett. 95, 217002 (2005).

Covalency Effects in the Magnetic Form Factor of Ir in K₂IrCl₆, J. W. Lynn, G. Shirane, and M. Blume, Phys. Rev. Lett. 37, 154 (1976).

4d materials;  Ruthenates

Phase Diagram of a-RuCl₃ in an in-plane Magnetic Field, J. A. Sears, Y. Zhao, Z. Xu, J. W. Lynn, and Young-June Kim, Phys. Rev. B 95, 180411(R) (2017).

Spin Dynamics and Two-dimensional Correlations in an FCC Antiferromagnetic Sr₂YRuO₆, S. M. Disseler, J. W. Lynn, R. F. Jardim, M. S. Torikachvili, and E. Granado, Phys. Rev. B 93, 140407(R) (2016).

Two-Dimensional Magnetic Correlations and Partial Long-Range Order in Geometrically Frustrated Sr₂YRuO₆, E. Granado, J. W. Lynn, R. F. Jardim, and M. Torikachvili, Phys. Rev. Lett. 110, 017202 (2013).

Spin-valve Effect and Magnetoresistivity in Single Crystalline Ca₃Ru₂O₇, W. Bao, Z. Q. Mao, Z. Qu, and J. W. Lynn, Phys. Rev. Lett. 100, 247203 (2008).

Unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio in double layered ruthenates (Sr_1-xCa_x)₃Ru₂O₇, Z. Qu, L. Spinu, H. Q. Yuan, V. Dobrosavljeviuc, W. Bao, J. W. Lynn, M. Nicklas, J. Peng, T. J. Liu, D. Fobes, E. Flesch, and Z. Q. Mao, Phys. Rev. B 78, 180407(R) (2008).

Structure and Magnetism of Single Crystal Sr₄Ru₃O₁₀:  A Ferromagnetic Triple-Layer Ruthenate, M. K. Crawford, R. L. Harlow, W. Marshall, Z. Li, G. Cao, R. L. Lindstrom, Q. Huang, and J. W. Lynn, Phys. Rev. B 65, 214412 (2002).

Synthesis and crystal structure of La₃RuO₇, P. Khalifah, Q. Huang, J. W. Lynn, R. W. Erwin, and R. J. Cava, Materials Research Bulletin 35, 1 (2000). 

Oxygen Displacements and Search for Magnetic Order in Sr₃Ru₂O₇, Q. Huang, J. W. Lynn, R. W. Erwin, J. Jarupatrakorn, and R. J. Cava, Phys. Rev. B 58, 8515 (1998).

5f materials;  Hidden order in URu₂Si₂

Orbital-selective Kondo-lattice and Enigmatic f-electrons emerging from inside the Antiferromagnetic Phase of a Heavy Fermion, Ioannis Giannakis, Justin Leshen, Mariam Kavai, Sheng Ran, Shanta R. Saha, Y. Zhao, Z. Xu, J. W. Lynn, Nicholas P. Butch, and Pegor Aynajian, Sci. Adv. 5, eaaw9061 (2019).

High temperature singlet-based magnetism from Hund's rule correlations, Lin Miao,Rourav Basak, Sheng Ran, Yishuai Xu, Haowei He, Jonathan D. Denlinger, Yi-De Chuang, Y. Zhao, Z. Xu, J. W. Lynn, J. R. Jeffries, S. R. Saha, Ioannis Giannakis, Pegor Aynajian, Chang-Jong Kang, Yilin Wang, Gabriel Kotliar, Nicholas P. Butch, L. Andrew Wray, Nature Communications 10, 644 (2019).

Distinct magnetic spectra in the hidden order and antiferromagnetic phases in URu_2-xFe_xSi₂, Nicholas P. Butch, Sheng Ran, Inho Jeon, Noravee Kanchanavatee, Kevin Huang, Alexander Breindel, M. Brian Maple, Ryan L. Stillwell, Yang Zhao, Leland Harriger, and Jeffrey W. Lynn, Phys. Rev. B 94, 201102 (2016).

Chemical Pressure Tuning of URu₂Si₂ via Isoelectronic Substitution of Ru with Fe, Pinaki Das, N. Kanchanavatee, J. S. Helton, K. Huang, R. E. Baumbach, E. D. Bauer, B. D. White, V. W. Burnett, M. B. Maple, J.W. Lynn, and M. Janoschek, Phys. Rev. B 91, 085122 (2015).

Symmetry and Correlations Underlying Hidden Order in URu₂Si₂, Nicholas P. Butch, Michael E. Manley, Jason R. Jeffries, Marc Janoschek, Kevin Huang, M. Brian Maple, Ayman H. Said, Bogdan M. Leu, and Jeffrey W. Lynn, Phys. Rev. B 91, 035128 (2015).

Absence of a static in-plane magnetic moment in the "hidden-order" phase of URu₂Si₂, P. Das, R. E. Baumbach, E. D. Bauer, K. Huang, M. B. Maple, Y. Zhao, J. Helton, J. W. Lynn, and M. Janoschek, New J. Phys. 15, 053031(2013).

Antiferromagnetic Critical Pressure in URu₂Si₂ under Hydrostatic Conditions, N. P. Butch, J. R. Jeffries, S. X. Chi, J. B. Leão, and J. W. Lynn, and M. B. Maple, Phys. Rev. B 82, 060408(R) (2010).

Non-Fermi Liquid Behavior and Quantum Criticality in Sc_1-xU_xPd₃ and URu_2-xRe_xSi₂, M. B. Maple, N. P. Butch, E. D. Bauer, V. S. Zapf, P.-C. Ho, S. D. Wilson , P. Dai, D. T. Adroja, S.-H. Lee, J.-H. Chung, J. W. Lynn, Physica B  378-380, 911 (2006).

Spin Ice, Magnetic Monopoles, and Spin Liquids

Magnetic Monopoles are spin excitaitons in spin-ice, and as there is no long range order these are also topoloigcal excitations of a kind:

Observation of Magnetic Monopoles in Spin Ice, Hiroaki Kadowaki, Naohiro Doi, Yuji Aoki, Yoshikazu Tabata, Taku J. Sato, J. W. Lynn, K. Matsuhira, and Z. Hiroi,  J. Phys. Soc. Japan 78, 103706 (2009).

Quantum Spin Fluctuations in the Spin Liquid State of Tb₂Ti₂O₇, Hiroshi Takatsu, Hiroaki Kadowaki, Taku J. Sato, Jeffrey W. Lynn, Yoshikazu Tabata, Terno Yamakaki, and Kazuyuki Matsuhira, J. Phys. Cond. Matr. 24, 052201 (2012).

Quadrupole Order in the Frustrated Pyrochlore Tb_2+xTi_2−xO_7+y, H. Takatsu, S. Onoda, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fåk, J. Ollivier, J. W. Lynn, T. Taniguchi, M. Wakita, and H. Kadowaki, Phys. Rev. Lett. 116, 217201 (2016).

Spin correlations of quantum-spin-liquid and quadrupole-ordered states of Tb_2+xTi_2-xO_7+y, Hiroaki Kadowaki, Mika Wakita, Björn Fåk, Jacques Ollivier, Seiko Ohira-Kawamura, Kenji M Kofu-Nakajima, and Jeffrey W. Lynn, Phys. Rev. B 99, 014406 (2019).

Absence of Magnetic Order in the Spin Liquid Candidate Ca₃Cu₂GeV₂O₁₂, Joey A. Lussier, Brooke Richtik, Cole Mauws, Jeffrey W. Lynn, and Chris R. Wiebe, J. Phys.: Condens. Matter 32, 134001 (2020).

Materializing Rival Ground States in the Barlowite Family of Kagome Magnets: Quantum Spin Liquid, Spin Ordered, and Valence Bond Crystal States, Rebecca W. Smaha, Wei He, Jack Mingde Jiang, Jiajia Wen, Yi-Fan Jiang, John P. Sheckelton, Charles J. Titus, Suyin Grass Wang, Yu-Sheng Chen, Simon J. Teat, Adam A. Aczel, Yang Zhao, Guangyong Xu, Jeffrey W. Lynn, Hong-Chen Jiang and Young S. Lee, Nature Partner Journals: Quantum Materials 5, 23 (2020).

Universal Dynamics of Magnetic Monopoles in Two-dimensional Kagome Ice, Hiroshi Takatsu, Kazuki Goto, Taku J. Sato, Jeffrey W. Lynn, Kazuyuki Matsubayashi, Yoshiya Uwatoko, Ryuji Higashinaka, Kazuyuki Matsuhira, Zenji Hiroi, and Hiroaki Kadowaki, J.  Phys. Soc. Jpn. 90, 123705 (2021).

Magnetic ground state of the Kitaev Na₂Co₂TeO₆ spin liquid candidate, Weiliang Yao, Yang Zhao, Yiming Qiu, Christian Balz, J. Ross Stewart, Jeffrey W. Lynn, and Yuan Li, Phys. Rev. Research 5, L022045 (2023).

         See Monopoles and Related Systems

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