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Speaker: Kota Mitsumoto (IIS, UTokyo)
Time & Date: 13:00 – 14:00, September 22, 2023 (JST)
Place: Hybrid (Room A614, ISSP / Zoom meeting)
Title: Spin-lattice glass transition without quenched disorder on
pyrochlore magnet
Abstract:
In the community of magnetism, it has been generally assumed that spin
glass transitions occur due to frustration from random interactions,
so-called quenched disorder. However, disorder-free spin glass
transitions are observed experimentally in a geometrically frustrated
pyrochlore magnet. So far, there are no convincing theoretical
explanations for the mechanism of this spin glass transition without
quenched disorder.
A recent experiment suggested that lattice distortions play important
roles in the spin glass transition on the prototypical geometrically
frustrated spin glass Y2Mo2O7[1]. This lattice distortion results from
the selection of the electron orbitals[2], i.e., Jahn-Teller
distortion. Being motivated by the experiment, we introduced a model
which includes not only the spin degrees of freedom but also the
lattice distortions as dynamical variables. This model doesn’t include
any quenched disorder, but both spins and lattice distortions are
geometrically frustrated. We performed extensive numerical simulations
for the model and analyzed a mean-field model which can be solved
exactly in the infinite dimension.
In the numerical simulations[3], we found that spins and lattice
distortions simultaneously freeze at a common finite temperature. Both
degrees of freedom do not exhibit any long range order below the
freezing temperature. In the mean-field analysis in the spherical
limit using the replica method[4], we found that replica symmetry
breaking appears only in the phase where both spins and lattice
distortions are frozen, implying that a complex free-energy landscape
is induced by the spin-lattice coupling
[1] P. M. Thygesen, et al., Phys. Rev. Lett. 118, 067201 (2017)
[2] KM, C. Hotta and H. Yoshino, Phys. Rev. Research 4, 033157 (2022)
[3] KM, C. Hotta and H. Yoshino, Phys. Rev. Lett. 124, 087201 (2020)
[4] KM and H. Yoshino, Phys. Rev. B 107, 054412 (2023)
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Satoshi Morita (森田 悟史)
Faculty of Science and Technology, Keio University
smorita.github.io/
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