Institute Affiliations

All Publications

  • Emergence of spin singlets with inhomogeneous gaps in the kagome lattice Heisenberg antiferromagnets Zn-barlowite and herbertsmithite NATURE PHYSICS Wang, J., Yuan, W., Singer, P. M., Smaha, R. W., He, W., Wen, J., Lee, Y. S., Imai, T. 2021
  • Site-specific structure at multiple length scales in kagome quantum spin liquid candidates PHYSICAL REVIEW MATERIALS Smaha, R. W., Boukahil, I., Titus, C. J., Jiang, J., Sheckelton, J. P., He, W., Wen, J., Vinson, J., Wang, S., Chen, Y., Teat, S. J., Devereaux, T. P., Das Pemmaraju, C., Lee, Y. S. 2020; 4 (12)
  • Impact of the Lattice on Magnetic Properties and Possible Spin Nematicity in the S=1 Triangular Antiferromagnet NiGa2S4 PHYSICAL REVIEW LETTERS Valentine, M. E., Higo, T., Nambu, Y., Chaudhuri, D., Wen, J., Broholm, C., Nakatsuji, S., Drichko, N. 2020; 125 (19): 197201


    NiGa_{2}S_{4} is a triangular lattice S=1 system with strong two dimensionality of the lattice, actively discussed as a candidate to host spin-nematic order brought about by strong quadrupole coupling. Using Raman scattering spectroscopy we identify a phonon of E_{g} symmetry which can modulate magnetic exchange J_{1} and produce quadrupole coupling. Additionally, our Raman scattering results demonstrate a loss of local inversion symmetry on cooling, which we associate with sulfur vacancies. This will lead to disordered Dzyaloshinskii-Moriya interactions, which can prevent long-range magnetic order. Using magnetic Raman scattering response we identify 160 K as a temperature of an upturn of magnetic correlations. The temperature range below 160 K, but above 50 K where antiferromagnetic correlations start to increase, is a candidate for spin-nematic regime.

    View details for DOI 10.1103/PhysRevLett.125.197201

    View details for Web of Science ID 000583639600014

    View details for PubMedID 33216581

  • Anomalous Hall and Nernst effects in epitaxial films of topological kagome magnet Fe3Sn2 PHYSICAL REVIEW MATERIALS Khadka, D., Thapaliya, T. R., Parra, S., Wen, J., Need, R., Kikkawa, J. M., Huang, S. X. 2020; 4 (8)
  • Kondo physics in antiferromagnetic Weyl semimetal Mn3+x Sn1-x films. Science advances Khadka, D., Thapaliya, T. R., Hurtado Parra, S., Han, X., Wen, J., Need, R. F., Khanal, P., Wang, W., Zang, J., Kikkawa, J. M., Wu, L., Huang, S. X. 2020; 6 (35): eabc1977


    Topology and strong electron correlations are crucial ingredients in emerging quantum materials, yet their intersection in experimental systems has been relatively limited to date. Strongly correlated Weyl semimetals, particularly when magnetism is incorporated, offer a unique and fertile platform to explore emergent phenomena in novel topological matter and topological spintronics. The antiferromagnetic Weyl semimetal Mn3Sn exhibits many exotic physical properties such as a large spontaneous Hall effect and has recently attracted intense interest. In this work, we report synthesis of epitaxial Mn3+x Sn1-x films with greatly extended compositional range in comparison with that of bulk samples. As Sn atoms are replaced by magnetic Mn atoms, the Kondo effect, which is a celebrated example of strong correlations, emerges, develops coherence, and induces a hybridization energy gap. The magnetic doping and gap opening lead to rich extraordinary properties, as exemplified by the prominent DC Hall effects and resonance-enhanced terahertz Faraday rotation.

    View details for DOI 10.1126/sciadv.abc1977

    View details for PubMedID 32923648

  • High quality epitaxial thin films and exchange bias of antiferromagnetic Dirac semimetal FeSn APPLIED PHYSICS LETTERS Khadka, D., Thapaliya, T. R., Wen, J., Need, R. F., Huang, S. X. 2020; 117 (3)

    View details for DOI 10.1063/5.0011497

    View details for Web of Science ID 000554944400001

  • Materializing rival ground states in the barlowite family of kagome magnets: quantum spin liquid, spin ordered, and valence bond crystal states NPJ QUANTUM MATERIALS Smaha, R. W., He, W., Jiang, J., Wen, J., Jiang, Y., Sheckelton, J. P., Titus, C. J., Wang, S., Chen, Y., Teat, S. J., Aczel, A. A., Zhao, Y., Xu, G., Lynn, J. W., Jiang, H., Lee, Y. S. 2020; 5 (1)
  • Materializing rival ground states in the barlowite family of kagome magnets: quantum spin liquid, spin ordered, and valence bond crystal states. npj quantum materials Smaha, R. W., He, W., Jiang, J. M., Wen, J., Jiang, Y., Sheckelton, J. P., Titus, C. J., Wang, S. G., Chen, Y., Teat, S. J., Aczel, A. A., Zhao, Y., Xu, G., Lynn, J. W., Jiang, H., Lee, Y. S. 2020; 5 (1)


    The spin- 1 2 kagome antiferromagnet is considered an ideal host for a quantum spin liquid (QSL) ground state. We find that when the bonds of the kagome lattice are modulated with a periodic pattern, new quantum ground states emerge. Newly synthesized crystalline barlowite (Cu4(OH)6FBr) and Zn-substituted barlowite demonstrate the delicate interplay between singlet states and spin order on the spin- 1 2 kagome lattice. Comprehensive structural measurements demonstrate that our new variant of barlowite maintains hexagonal symmetry at low temperatures with an arrangement of distorted and undistorted kagome triangles, for which numerical simulations predict a pinwheel valence bond crystal (VBC) state instead of a QSL. The presence of interlayer spins eventually leads to an interesting pinwheel q = 0 magnetic order. Partially Zn-substituted barlowite (Cu3.44Zn0.56(OH)6FBr) has an ideal kagome lattice and shows QSL behavior, indicating a surprising robustness of the QSL against interlayer impurities. The magnetic susceptibility is similar to that of herbertsmithite, even though the Cu2+ impurities are above the percolation threshold for the interlayer lattice and they couple more strongly to the nearest kagome moment. This system is a unique playground displaying QSL, VBC, and spin order, furthering our understanding of these highly competitive quantum states.

    View details for PubMedID 33072886

  • Site-Specific Structure at Multiple Length Scales in Kagome Quantum Spin Liquid Candidates. Physical review materials Smaha, R. W., Boukahil, I., Titus, C. J., Jiang, J. M., Sheckelton, J. P., He, W., Wen, J., Vinson, J., Wang, S. G., Chen, Y. S., Teat, S. J., Devereaux, T. P., Pemmaraju, C. D., Lee, Y. S. 2020; 4 (12)


    Realizing a quantum spin liquid (QSL) ground state in a real material is a leading issue in condensed matter physics research. In this pursuit, it is crucial to fully characterize the structure and influence of defects, as these can significantly affect the fragile QSL physics. Here, we perform a variety of cutting-edge synchrotron X-ray scattering and spectroscopy techniques, and we advance new methodologies for site-specific diffraction and L-edge Zn absorption spectroscopy. The experimental results along with our first-principles calculations address outstanding questions about the local and long-range structures of the two leading kagome QSL candidates, Zn-substituted barlowite (Cu3Zn x Cu1-x (OH)6FBr) and herbertsmithite (Cu3Zn(OH)6Cl2). On all length scales probed, there is no evidence that Zn substitutes onto the kagome layers, thereby preserving the QSL physics of the kagome lattice. Our calculations show that antisite disorder is not energetically favorable and is even less favorable in Zn-barlowite compared to herbertsmithite. Site-specific X-ray diffraction measurements of Zn-barlowite reveal that Cu2+ and Zn2+ selectively occupy distinct interlayer sites, in contrast to herbertsmithite. Using the first measured Zn L-edge inelastic X-ray absorption spectra combined with calculations, we discover a systematic correlation between the loss of inversion symmetry from pseudo-octahedral (herbertsmithite) to trigonal prismatic coordination (Zn-barlowite) with the emergence of a new peak. Overall, our measurements suggest that Zn-barlowite has structural advantages over herbertsmithite that make its magnetic properties closer to an ideal QSL candidate: its kagome layers are highly resistant to nonmagnetic defects while the interlayers can accommodate a higher amount of Zn substitution.

    View details for DOI 10.1103/physrevmaterials.4.124406

    View details for PubMedID 34095744

    View details for PubMedCentralID PMC8174140

  • Observation of two types of charge-density-wave orders in superconducting La2-xSrxCuO4. Nature communications Wen, J., Huang, H., Lee, S., Jang, H., Knight, J., Lee, Y. S., Fujita, M., Suzuki, K. M., Asano, S., Kivelson, S. A., Kao, C., Lee, J. 2019; 10 (1): 3269


    The discovery of charge- and spin-density-wave (CDW/SDW) orders in superconducting cuprates has altered our perspective on the nature of high-temperature superconductivity (SC). However, it has proven difficult to fully elucidate the relationship between the density wave orders and SC. Here, using resonant soft X-ray scattering, we study the archetypal cuprate La2-xSrxCuO4 (LSCO) over a broad doping range. We reveal the existence of two types of CDW orders in LSCO, namely CDW stripe order and CDW short-range order (SRO). While the CDW-SRO is suppressed by SC, it is partially transformed into the CDW stripe order with developing SDW stripe order near the superconducting Tc. These findings indicate that the stripe orders and SC are inhomogeneously distributed in the superconducting CuO2 planes of LSCO. This further suggests a new perspective on the putative pair-density-wave order that coexists with SC, SDW, and CDW orders.

    View details for DOI 10.1038/s41467-019-11167-z

    View details for PubMedID 31332190

  • The Search for the Quantum Spin Liquid in Kagome Antiferromagnets CHINESE PHYSICS LETTERS Wen, J., Lee, Y. S. 2019; 36 (5)
  • Magnetic Excitations of the Classical Spin Liquid MgCr2O4 PHYSICAL REVIEW LETTERS Bai, X., Paddison, J. M., Kapit, E., Koohpayeh, S. M., Wen, J., Dutton, S. E., Savici, A. T., Kolesnikov, A. I., Granroth, G. E., Broholm, C. L., Chalker, J. T., Mourigal, M. 2019; 122 (9): 097201


    We report a comprehensive inelastic neutron-scattering study of the frustrated pyrochlore antiferromagnet MgCr_{2}O_{4} in its cooperative paramagnetic regime. Theoretical modeling yields a microscopic Heisenberg model with exchange interactions up to third-nearest neighbors, which quantitatively explains all of the details of the dynamic magnetic response. Our work demonstrates that the magnetic excitations in paramagnetic MgCr_{2}O_{4} are faithfully represented in the entire Brillouin zone by a theory of magnons propagating in a highly correlated paramagnetic background. Our results also suggest that MgCr_{2}O_{4} is proximate to a spiral spin-liquid phase distinct from the Coulomb phase, which has implications for the magnetostructural phase transition in MgCr_{2}O_{4}.

    View details for DOI 10.1103/PhysRevLett.122.097201

    View details for Web of Science ID 000460669200008

    View details for PubMedID 30932548

  • Interconnected Signatures of Quantum Spin Liquid Physics Across the Barlowite Family of Quantum Magnets Smaha, R., He, W., Jiang, J., Titus, C., Wen, J., Lee, Y. INT UNION CRYSTALLOGRAPHY. 2019: A122
  • Universal geometric frustration in pyrochlores NATURE COMMUNICATIONS Trump, B. A., Koohpayeh, S. M., Livi, K. T., Wen, J., Arpino, K. E., Ramasse, Q. M., Brydson, R., Feygenson, M., Takeda, H., Takigawa, M., Kimura, K., Nakatsuji, S., Broholm, C. L., McQueen, T. M. 2018; 9: 2619


    Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report the observation of structural instability present in the pyrochlores A2Zr2O6O' (A = Pr, La) and Yb2Ti2O6O', that exists despite ideal stoichiometry, ideal cation-ordering, the absence of lone pair effects, and a lack of magnetic order. Though these materials appear to have good long-range order, local structure probes find displacements, of the order of 0.01 nm, within the pyrochlore framework. The pattern of displacements of the A2O' sublattice mimics the entropically-driven fluxional motions characteristic of and well-known in the silica mineral β-cristobalite. The universality of such displacements within the pyrochlore structure adds to the known structural diversity and explains the extreme sensitivity to composition found in quantum spin ices and the lack of ferroelectric behavior in pyrochlores.

    View details for DOI 10.1038/s41467-018-05033-7

    View details for Web of Science ID 000437417600006

    View details for PubMedID 29976983

    View details for PubMedCentralID PMC6033937

  • Enhancement and destruction of spin-Peierls physics in a one-dimensional quantum magnet under pressure PHYSICAL REVIEW B Rotundu, C. R., Wen, J., He, W., Choi, Y., Haskel, D., Lee, Y. S. 2018; 97 (5)
  • Synthesis dependent properties of barlowite and Zn-substituted barlowite Journal of Solid State Chemistry Smaha, R. W., He, W., Sheckelton, J. P., Wen, J., Lee, Y. S. 2018; 268: 123-129
  • Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr2Zr2O7 PHYSICAL REVIEW LETTERS Wen, J., Koohpayeh, S. M., Ross, K. A., Trump, B. A., McQueen, T. M., Kimura, K., Nakatsuji, S., Qiu, Y., Pajerowski, D. M., Copley, J. R., Broholm, C. L. 2017; 118 (10)


    Inelastic neutron scattering reveals a broad continuum of excitations in Pr_{2}Zr_{2}O_{7}, the temperature and magnetic field dependence of which indicate a continuous distribution of quenched transverse fields (Δ) acting on the non-Kramers Pr^{3+} crystal field ground state doublets. Spin-ice correlations are apparent within 0.2 meV of the Zeeman energy. A random phase approximation provides an excellent account of the data with a transverse field distribution ρ(Δ)∝(Δ^{2}+Γ^{2})^{-1}, where Γ=0.27(1)  meV. Established during high temperature synthesis due to an underlying structural instability, it appears disorder in Pr_{2}Zr_{2}O_{7} actually induces a quantum spin liquid.

    View details for DOI 10.1103/PhysRevLett.118.107206

    View details for Web of Science ID 000396047400010

    View details for PubMedID 28339241

  • Correlated impurities and intrinsic spin-liquid physics in the kagome material herbertsmithite PHYSICAL REVIEW B Han, T., Norman, M. R., Wen, J., Rodriguez-Rivera, J. A., Helton, J. S., Broholm, C., Lee, Y. S. 2016; 94 (6)
  • Disorder from order among anisotropic next-nearest-neighbor Ising spin chains in SrHo2O4 PHYSICAL REVIEW B Wen, J., Tian, W., Garlea, V. O., Koohpayeh, S. M., McQueen, T. M., Li, H., Yan, J., Rodriguez-Rivera, J. A., Vaknin, D., Broholm, C. L. 2015; 91 (5)
  • Quantum fluctuations in spin-ice-like Pr2Zr2O7 NATURE COMMUNICATIONS Kimura, K., Nakatsuji, S., Wen, J., Broholm, C., Stone, M. B., Nishibori, E., Sawa, H. 2013; 4: 1934


    Spin ice is a magnetic analog of H2O ice that harbors dense static disorder. Dipolar interactions between classical spins yield a frozen frustrated state with residual configurational Pauling entropy and emergent magnetic monopolar quasiparticles. Introducing quantum fluctuations is of great interest as this could melt spin ice and allow coherent propagation of monopoles. Here, we report experimental evidence for quantum dynamics of magnetic monopolar quasiparticles in a new class of spin ice based on exchange interactions, Pr2Zr2O7. Narrow pinch point features in otherwise diffuse elastic neutron scattering reflects adherence to a divergence-free constraint for disordered spins on long time scales. Magnetic susceptibility and specific heat data correspondingly show exponentially activated behaviors. In sharp contrast to conventional ice, however, >90% of the neutron scattering is inelastic and devoid of pinch points furnishing evidence for magnetic monopolar quantum fluctuations.

    View details for DOI 10.1038/ncomms2914

    View details for Web of Science ID 000323624100001

    View details for PubMedID 23770751