*Spin-Orbit Coupling and Topological
Systems*

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.

**Half-Heusler Topological Insulators**

In the so-called Z_{2} 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 on which we have been collaborating. The
antiferromagnetism breaks time reversal and translational symmetries but
preserves the combination, leading to a new type of
system, the antiferromagnetic topological insulator.

**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).

**5d****
sytems; Iridates**

**Influence of Electron-doping on the Ground State of (Sr**_{1-x}**La**_{x})_{2}**IrO**_{4},
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 Sr _{3}(Ir_{1-x}Ru_{x})_{2}O_{7},** 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)

_{2}MIn_{8} (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)In**

**
Covalency Effects in the Magnetic Form Factor of Ir in K**

**4d****
materials; Ruthenates**

**Spin Dynamics and Two-dimensional Correlations in an FCC
Antiferromagnetic Sr**_{2}**YRuO _{6},**
S. M. Disseler, J. W. Lynn, R. F. Jardim, M. S. Torikachvili, and E.
Granado,
Phys. Rev.
B 93, 140407(R) (2016).

_{2}YRuO_{6},
E. Granado, J. W. Lynn, R. F. Jardim, and M. Torikachvili,
*
Phys. Rev.
Lett. 110,
017202 (2013).*

_{3}Ru_{2}O_{7},
W. Bao, Z. Q. Mao, Z. Qu, and J. W. Lynn,
*Phys. Rev. Lett. ***100**,
247203 (2008).

_{1-x}Ca_{x})_{3}Ru_{2}O_{7},
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).

_{4}Ru_{3}O_{10}:
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).

_{3}RuO_{7}, P. Khalifah, Q.
Huang, J. W. Lynn, R. W. Erwin, and R. J. Cava,
Materials Research Bulletin
35, 1 (2000).

_{3}Ru_{2}O_{7},
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 URu**_{2}**Si**_{2}

**Distinct magnetic spectra in the hidden order and antiferromagnetic
phases in URu**_{2-x}**Fe**_{x}**Si**_{2},
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, (submitted).

**Chemical Pressure Tuning of URu**_{2}**Si**_{2}**
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 URu**_{2}**Si**_{2},
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 URu**_{2}**Si**_{2},
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).

_{2}Si_{2} 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)

_{1-x}U* _{x}*Pd