B4: Magnetic resonance spectroscopy on quantum spin liquids and Weyl semimetals
Norbert Büttgen, Hans-Albrecht Krug von Nidda
Electron spin resonance and nuclear magnetic resonance serve as site selective probes of the dynamic susceptibility in constrained quantum matter. In triangular and Kitaev magnets these techniques are applied in search for signatures of fractionalized excitations and entanglement characteristic of quantum-spin liquids. In magnetic topological semimetals anomalies in the electronic density of states at the Fermi level and their variation with magnetic field can be resolved, complementing spectroscopic studies in other projects in revealing information about band topology.
Publications
2024 |
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Hemmida, M.; Masell, J.; Karube, K.; Ehlers, D.; von Nidda, H. -A. Krug; Tsurkan, V.; Tokura, Y.; Taguchi, Y.; Kézsmárki, I. Role of magnetic anisotropy in the antiskyrmion-host schreibersite magnets Journal Article Phys. Rev. B 110, 054416, 2024. @article{hemmida_role_2024, | |
Büttgen, N.; von Nidda, H. -A. Krug Magnetic resonance in quantum spin chains with competing exchange interactions Journal Article J. Phys. A: Math. Theor. 57, 313001, 2024. @article{buttgen_magnetic_2024, Based on a previous review on magnetic resonance in quantum spin chains (Krug von Nidda et al 2010 Eur. Phys. J. Spec. Top. 180 161–89) we report on further development in this field with special focus on transition–metal oxides and halogenides consisting of quasi one–dimensional spin systems, where both intra–and inter–chain exchange interaction may give rise to frustration effects and higher–order anisotropic exchange contributions like the Dzyaloshinskii–Moriya interaction become decisive for the formation of the magnetic ground state. Selected examples show how NMR and ESR contribute valuable information on the magnetic phases and exchange interactions involved: LiCuVO4 with competing nearest neighbour and next–nearest neighbour intra–chain exchange, LiCu2O2 with complex zig–zag chains, and Cs2CuCl4 where the chains form a triangular lattice with the inter–chain interaction weaker but of the same order of magnitude than the intra–chain interaction. The so called paper–chain compound Ba3Cu3In4O12, where each successive pair of CuO4 plaquettes is rotated by 90° with respect to its predecessor along the c–direction like in a paper–chain, provides an interesting topology of frustrated intra–chain exchange interactions. Finally, a few dimer systems are considered. | |
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, 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. | |
2023 |
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Tóth, B.; Amelin, K.; Rõõm, T.; Nagel, U.; Bauernfeind, A.; Tsurkan, V.; Prodan, L.; von Nidda, H. -A. Krug; Scheffler, M.; Kézsmárki, I.; others, Broadband magnetic resonance spectroscopy in MnSc2S4 Journal Article Sci. Rep. 13, 11069, 2023, Publisher: Nature Publishing Group UK London. @article{toth_broadband_2023, Recent neutron scattering experiments suggested that frustrated magnetic interactions give rise to antiferromagnetic spiral and fractional skyrmion lattice phases in MnSc2S4. Here, to trace the signatures of these modulated phases, we studied the spin excitations of MnSc2S4 by THz spectroscopy at 300 mK and in magnetic fields up to 12 T and by broadband microwave spectroscopy at various temperatures up to 50 GHz. We found a single magnetic resonance with frequency linearly increasing in field. The small deviation of the Mn2+ ion g-factor from 2 |