2024
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Tang, N.; Gen, M.; Rotter, M.; Man, H.; Matsuhira, K.; Matsuo, A.; Kindo, K.; Ikeda, A.; Matsuda, Y.; Gegenwart, P.; Nakatsuji, S.; Kohama, Y. Crystal field magnetostriction of spin ice under ultrahigh magnetic fields Journal Article Phys. Rev. B 110, 214414 (2024). @article{tang_crystal_2024,
title = {Crystal field magnetostriction of spin ice under ultrahigh magnetic fields},
author = {N. Tang and M. Gen and M. Rotter and H. Man and K. Matsuhira and A. Matsuo and K. Kindo and A. Ikeda and Y. Matsuda and P. Gegenwart and S. Nakatsuji and Y. Kohama},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.214414},
doi = {10.1103/PhysRevB.110.214414},
year = {2024},
date = {2024-12-09},
urldate = {2024-12-01},
journal = {Phys. Rev. B},
volume = {110},
number = {21},
pages = {214414},
abstract = {We present a comprehensive study of the magnetoelastic properties of the Ising pyrochlore oxide Ho2Ti2O7, known as spin ice, by means of high-field magnetostriction measurements and numerical calculations. When a magnetic field is applied along the crystallographic ⟨111⟩ axis, the longitudinal magnetostriction exhibits a broad maximum in the low-field regime around 30 T, followed by a dramatic lattice contraction due to crystal-field (CF) level crossing at 𝐵cf∼65 T. The transverse magnetostriction exhibits a contrasting behavior, highlighting the anisotropic nature of the CF striction. By applying a magnetic field at varying sweep rates, we identify distinct timescales of spin dynamics that are relevant to monopole formation and annihilation, as well as CF-phonon dynamics. Our mean-field calculations, based on a point-charge model, successfully reproduce the overall magnetostriction behavior, revealing the competition between the exchange striction and CF striction. A signature of the CF level crossing is also observed through adiabatic magnetocaloric-effect measurements, consistent with our magnetostriction data.},
keywords = {B3, B5},
pubstate = {published},
tppubtype = {article}
}
We present a comprehensive study of the magnetoelastic properties of the Ising pyrochlore oxide Ho2Ti2O7, known as spin ice, by means of high-field magnetostriction measurements and numerical calculations. When a magnetic field is applied along the crystallographic ⟨111⟩ axis, the longitudinal magnetostriction exhibits a broad maximum in the low-field regime around 30 T, followed by a dramatic lattice contraction due to crystal-field (CF) level crossing at 𝐵cf∼65 T. The transverse magnetostriction exhibits a contrasting behavior, highlighting the anisotropic nature of the CF striction. By applying a magnetic field at varying sweep rates, we identify distinct timescales of spin dynamics that are relevant to monopole formation and annihilation, as well as CF-phonon dynamics. Our mean-field calculations, based on a point-charge model, successfully reproduce the overall magnetostriction behavior, revealing the competition between the exchange striction and CF striction. A signature of the CF level crossing is also observed through adiabatic magnetocaloric-effect measurements, consistent with our magnetostriction data. |  |
Kumar, H.; Köpf, M.; Telang, P.; Bura, N.; Jesche, A.; Gegenwart, P.; Kuntscher, C. A. Optical conductivity of the metallic pyrochlore iridate Pr2Ir2O7: Influence of spin-orbit coupling and electronic correlations on the electronic structure Journal Article Phys. Rev. B 110, 035140 (2024). @article{kumar_optical_2024,
title = {Optical conductivity of the metallic pyrochlore iridate Pr_{2}Ir_{2}O_{7}: Influence of spin-orbit coupling and electronic correlations on the electronic structure},
author = {H. Kumar and M. Köpf and P. Telang and N. Bura and A. Jesche and P. Gegenwart and C. A. Kuntscher},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.035140},
doi = {10.1103/PhysRevB.110.035140},
year = {2024},
date = {2024-07-15},
urldate = {2024-07-01},
journal = {Phys. Rev. B},
volume = {110},
number = {3},
pages = {035140},
abstract = {The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr2Ir2O7 and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic Fd‾3m crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr2Ir2O7. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr2Ir2O7 is close to the Weyl semimetal phase.},
keywords = {A1, B5},
pubstate = {published},
tppubtype = {article}
}
The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr2Ir2O7 and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic Fd‾3m crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr2Ir2O7. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr2Ir2O7 is close to the Weyl semimetal phase. |  |
Hirschberger, M.; Szigeti, B. G.; Hemmida, M.; Hirschmann, M. M.; Esser, S.; Ohsumi, H.; Tanaka, Y.; Spitz, L.; Gao, S.; Kolincio, K. K.; Sagayama, H.; Nakao, H.; Yamasaki, Y.; Forró, L.; von Nidda, H. -A. Krug; Kézsmárki, I.; Arima, T.; Tokura, Y. Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet Journal Article npj Quantum Mater. 9, 45 (2024). @article{hirschberger_lattice-commensurate_2024,
title = {Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet},
author = {M. Hirschberger and B. G. Szigeti and M. Hemmida and M. M. Hirschmann and S. Esser and H. Ohsumi and Y. Tanaka and L. Spitz and S. Gao and K. K. Kolincio and H. Sagayama and H. Nakao and Y. Yamasaki and L. Forró and H. -A. Krug von Nidda and I. Kézsmárki and T. Arima and Y. Tokura},
doi = {10.1038/s41535-024-00654-2},
year = {2024},
date = {2024-05-23},
urldate = {2024-05-01},
journal = {npj Quantum Mater.},
volume = {9},
pages = {45},
abstract = {Skyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination of ferromagnetic resonance and REXS, penalizes placing a skyrmion core on a site of the atomic lattice. Under these conditions, a commensurate SkL, locked to the crystal lattice, is stable at finite temperatures – but gives way to a competing incommensurate ground state upon cooling. We discuss the role of Umklapp-terms in the Hamiltonian for the formation of this lattice-locked state, its magnetic space group, and the role of slight discommensurations, or (line) defects in the magnetic texture. We also contrast our findings with the case of SkLs in noncentrosymmetric material platforms.},
keywords = {B4, B5},
pubstate = {published},
tppubtype = {article}
}
Skyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination of ferromagnetic resonance and REXS, penalizes placing a skyrmion core on a site of the atomic lattice. Under these conditions, a commensurate SkL, locked to the crystal lattice, is stable at finite temperatures – but gives way to a competing incommensurate ground state upon cooling. We discuss the role of Umklapp-terms in the Hamiltonian for the formation of this lattice-locked state, its magnetic space group, and the role of slight discommensurations, or (line) defects in the magnetic texture. We also contrast our findings with the case of SkLs in noncentrosymmetric material platforms. | |
Reinhoffer, C.; Esser, S.; Esser, S.; Mashkovich, E.; Germanskiy, S.; Gegenwart, P.; Anders, F.; Loosdrecht, P. H. M.; Wang, Z. Strong Terahertz Third-Harmonic Generation by Kinetic Heavy Quasiparticles in CaRuO3 Journal Article Phys. Rev. Lett. 132, 196501 (2024). @article{reinhoffer_strong_2024,
title = {Strong Terahertz Third-Harmonic Generation by Kinetic Heavy Quasiparticles in CaRuO_{3}},
author = {C. Reinhoffer and S. Esser and S. Esser and E. Mashkovich and S. Germanskiy and P. Gegenwart and F. Anders and P. H. M. Loosdrecht and Z. Wang},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.132.196501},
doi = {10.1103/PhysRevLett.132.196501},
year = {2024},
date = {2024-05-08},
urldate = {2024-05-08},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {19},
pages = {196501},
abstract = {We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO_{3}, as a function of temperature, frequency, and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund’s coupling. Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles.},
keywords = {B1, B5},
pubstate = {published},
tppubtype = {article}
}
We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO3, as a function of temperature, frequency, and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund’s coupling. Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles. | |
