Browsing by Author "Li, Y"

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    Giant magnetic in-plane anisotropy and competing instabilities in Na3Co2SbO6
    (American Physical Society, 2022-12-02) Li, XT; Gu, YC; Chen, Y; Garlea, VO; Iida, K; Kamazawa, K; Li, YM; Deng, GC; Xiao, Q; Zheng, XQ; Ye, Z; Peng, YY; Zaliznyak, IA; Tranquada, JM; Li, Y
    We report magnetometry data obtained on twin-free single crystals of Na3Co2SbO6, which is considered a candidate material for realizing the Kitaev honeycomb model for quantum spin liquids. Contrary to a common belief that such materials can be modeled with the symmetries of an ideal honeycomb lattice, our data reveal a pronounced twofold symmetry and in-plane anisotropy of over 200%, despite the honeycomb layer’s tiny orthorhombic distortion of less than 0.2%. We further use magnetic neutron diffraction to elucidate a rich variety of field-induced phases observed in the magnetometry. These phases manifest themselves in the paramagnetic state as diffuse scattering signals associated with competing ferromagnetic and antiferromagnetic instabilities, consistent with a theory that also predicts a quantum spin liquid phase nearby. Our results call for theoretical understanding of the observed in-plane anisotropy and render Na3Co2SbO6 a promising ground for finding exotic quantum phases by targeted external tuning. © Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
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    Hidden magnetic excitation in the pseudogap phase of a high-T-c superconductor
    (Natural Publishing Group, 2010-11-11) Li, Y; Baledent, V; Yu, G; Barisic, N; Hradil, K; Mole, RA; Sidis, Y; Steffens, P; Zhao, X; Bourges, P; Greven, M
    The elucidation of the pseudogap phenomenon of the high-transition-temperature (high-T-c) copper oxides-a set of anomalous physical properties below the characteristic temperature T* and above T-c-has been a major challenge in condensed matter physics for the past two decades(1). Following initial indications of broken time-reversal symmetry in photoemission experiments(2), recent polarized neutron diffraction work demonstrated the universal existence of an unusual magnetic order below T* (refs 3, 4). These findings have the profound implication that the pseudogap regime constitutes a genuine new phase of matter rather than a mere crossover phenomenon. They are furthermore consistent with a particular type of order involving circulating orbital currents, and with the notion that the phase diagram is controlled by a quantum critical point(5). Here we report inelastic neutron scattering results for HgBa2CuO4+delta that reveal a fundamental collective magnetic mode associated with the unusual order, and which further support this picture. The mode's intensity rises below the same temperature T* and its dispersion is weak, as expected for an Ising-like order parameter(6). Its energy of 52-56 meV renders it a new candidate for the hitherto unexplained ubiquitous electron-boson coupling features observed in spectroscopic studies(7-10). © 2011, Nature Publishing Group
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    Highly anisotropic anomaly in the dispersion of the copper-oxygen bond-bending phonon in superconducting YBa2Cu3O7 from inelastic neutron scattering
    (American Physical Society, 2011-10-19) Raichle, M; Reznik, D; Lamago, D; Heid, R; Li, Y; Bakr, M; Ulrich, C; Hinkov, V; Hradil, K; Lin, CT; Keimer, B
    Motivated by predictions of a substantial contribution of the "buckling'' vibration of the CuO2 layers to d-wave superconductivity in the cuprates, we have performed an inelastic neutron scattering study of this phonon in an array of untwinned crystals of YBa2Cu3O7. The data reveal a pronounced softening of the phonon at the in-plane wave vector q = (0, 0.3) upon cooling below similar to 105 K, but no corresponding anomaly at q = (0.3,0). Based on the observed in-plane anisotropy, we argue that the electron-phonon interaction responsible for this anomaly supports an electronic instability associated with a uniaxial charge-density modulation and does not mediate d-wave superconductivity. © 2011, American Physical Society.
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    Insight of a phase compatible surface coating for long-durable Li-rich layered oxide cathode
    (John Wiley & Sons, Inc, 2019-07-28) Hu, SJ; Li, Y; Chen, YH; Peng, JM; Zhou, TF; Pang, WK; Didier, C; Peterson, VK; Wang, HQ; Li, QY; Guo, ZP
    Li-rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO2 and LiMn2O4; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high-energy lithium-ion batteries. Herein, hexagonal La0.8Sr0.2MnO3−y (LSM) is used as a protective and phase-compatible surface layer to stabilize the Li-rich layered Li1.2Ni0.13Co0.13Mn0.54O2 (LM) cathode material. The LSM is Mn O M bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM-coated LM delivers an enhanced reversible capacity of 202 mAh g−1 at 1 C (260 mA g−1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g−1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next-generation of high-energy Li-ion batteries. © 2019 Wiley-VCH Verlag GmbH & Co.
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    Preferred spin excitations in the bilayer iron-based superconductor CaKðFe0.96Ni0.04Þ4As4 with spin-vortex crystal order
    (American Physical Society, 2022-03-31) Liu, C; Bourges, P; Sidis, Y; He, GH; Bourdarot, F; Danilkin, SA; Ghosh, H; Ghosh, S; Ma, XY; Li, SL; Li, Y; Luo, HQ; Xie, T
    Spin-orbit coupling (SOC) is a key to understand the magnetically driven superconductivity in iron-based superconductors, where both local and itinerant electrons are present and the orbital angular momentum is not completely quenched. Here, we report a neutron scattering study on the bilayer compound CaK(Fe0.96Ni0.04)4As4 with superconductivity coexisting with a noncollinear spin-vortex crystal magnetic order that preserves the tetragonal symmetry of the Fe-Fe plane. In the superconducting state, two spin resonance modes with odd and even L symmetries due to the bilayer coupling are found similar to the undoped compound CaKFe4As4 but at lower energies. Polarization analysis reveals that the odd mode is c-axis polarized, and the low-energy spin anisotropy can persist to the paramagnetic phase at high temperature, which closely resembles other systems with in-plane collinear and c-axis biaxial magnetic orders. These results provide the missing piece of the puzzle on the SOC effect in iron-pnictide superconductors, and also establish a common picture of c-axis preferred magnetic excitations below Tc regardless of the details of magnetic pattern or lattice symmetry. © 2022 American Physical Society
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    Two characteristic energies in the low-energy magnetic response of the electron-doped high-temperature superconductor Nd(2-x)Ce(x)CuO(4+delta)
    (American Physical Society, 2010-11-11) Yu, G; Li, Y; Motoyama, EM; Hradil, K; Mole, RA; Greven, M
    Neutron scattering for Nd2-xCexCuO4+delta(x approximate to 0.155, T-c=25 K) reveals two distinct magnetic energy scales in the superconducting state: omega(1)approximate to 6.4 meV and omega(2)approximate to 4.5 meV. These magnetic energies agree quantitatively with the B-1g/B-2g and A(1g) features observed in electronic Raman scattering, where the former is believed to indicate the maximum superconducting gap and the origin of the latter has remained unexplained. The data are inconsistent with previous claims of the existence of a magnetic resonance mode near 10 meV, but consistent with a resonance at omega(2) and with the recently established universal ratio of resonance energy to superconducting gap in unconventional superconductors.[G. Yu et al., Nat. Phys. 5, 873 (2009)]. © 2010, American Physical Society
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    Two Ising-like magnetic excitations in a single-layer cuprate superconductor
    (Nature Publishing Group, 2012-05-01) Li, Y; Yu, G; Chan, MK; Baledent, V; Li, Y; Barisic, N; Zhao, X; Hradil, K; Mole, RA; Sidis, Y; Steffens, P; Bourges, P; Greven, M
    There exists increasing evidence that the phase diagram of the high-transition temperature (T(c)) cuprate superconductors is controlled by a quantum critical point. According to one distinct theoretical proposal, on decreasing the hole-carrier concentration a transition occurs to an ordered state with two circulating orbital currents per CuO(2) square. Below the 'pseudogap' temperature T* (T* > T(c)), the theory predicts a discrete order parameter and two weakly-dispersive magnetic excitations in structurally simple compounds which should be measurable by neutron scattering. Indeed, novel magnetic order and one such excitation were recently observed. Here, we demonstrate for tetragonal HgBa(2)CuO(4+delta) the existence of a second excitation with local character, consistent with the theory. The excitations mix with conventional antiferromagnetic fluctuations, which points towards a unifying picture of magnetism in the cuprates that will probably require a multi-band description. © 2012, Nature Publishing Group.