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Short-range order and increased transition temperature in LiVO2 with weakened trimer frustration
Authors:
K. Kojima,
N. Katayama,
Y. Matsuda,
M. Shiomi,
R. Ishii,
H. Sawa
Abstract:
Vanadium atoms in layered LiVO2 form in-plane periodic vanadium trimers at low temperatures, but the trimers appear randomly in the stacking direction because there are many trimer configurations with comparable lattice energy. We detailed an original modeling scheme to represent glassy states with a completely disordered trimer configuration in the stacking structure. Through PDF analysis using t…
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Vanadium atoms in layered LiVO2 form in-plane periodic vanadium trimers at low temperatures, but the trimers appear randomly in the stacking direction because there are many trimer configurations with comparable lattice energy. We detailed an original modeling scheme to represent glassy states with a completely disordered trimer configuration in the stacking structure. Through PDF analysis using this model, we show that the synthesis method can yield two types of low-temperature stacking structures: a completely disordered stacking structure and a short-range order in the stacking structure. The phase transition temperature of the former sample is about 15 K lower than that of the latter. We discuss that this is due to the strong trimer frustration that appears in the sample without short-range order, which suppresses the phase transition temperature, similar to the frustration effect in conventional spin systems.
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Submitted 10 January, 2023;
originally announced January 2023.
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Charge-ordered state satisfying the Anderson condition in LiRh2O4 arising from local dimer order
Authors:
Manabu Shiomi,
Keita Kojima,
Naoyuki Katayama,
Shin Maeda,
John A. Schneeloch,
Syunsuke Yamamoto,
Koudai Sugimoto,
Yukinori Ohta,
Despina Louca,
Yoshihiko Okamoto,
Hiroshi Sawa
Abstract:
We report on the charge-ordered structure of LiRh2O4 arising below the metal-insulator transition at 170 K. Structural studies using synchrotron X-rays have revealed that the charge-ordered states of Rh3+ and Rh4+ with dimerization are realized in the low-temperature phase below 170 K. Although the low-temperature ground state resembles that of CuIr2S4, a charge ordering pattern satisfying the And…
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We report on the charge-ordered structure of LiRh2O4 arising below the metal-insulator transition at 170 K. Structural studies using synchrotron X-rays have revealed that the charge-ordered states of Rh3+ and Rh4+ with dimerization are realized in the low-temperature phase below 170 K. Although the low-temperature ground state resembles that of CuIr2S4, a charge ordering pattern satisfying the Anderson condition is realized in LiRh2O4. Based on structural information such as the short-range order of dimers appearing above the transition temperature and the weakening of the correlation between rhodium one-dimensional chains appearing in the crystal structure, we argue that the Coulomb interaction plays an important role in determining the charge ordering patterns.
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Submitted 14 December, 2021; v1 submitted 13 December, 2021;
originally announced December 2021.
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Vanadium trimers randomly aligned along the c-axis direction in layered LiVO2
Authors:
K. Kojima,
N. Katayama,
S. Tamura,
M. Shiomi,
H. Sawa
Abstract:
Herein, we discuss the identification of vanadium trimers in layered LiVO2 and its sulfide analog of LiVS2 with two-dimensional triangular lattices. Our comprehensive structural studies using synchrotron X-ray diffraction experiments clarified that vanadium trimers are randomly aligned along the c-axis direction in LiVO2, while the long-range ordering of vanadium trimers along the c-axis direction…
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Herein, we discuss the identification of vanadium trimers in layered LiVO2 and its sulfide analog of LiVS2 with two-dimensional triangular lattices. Our comprehensive structural studies using synchrotron X-ray diffraction experiments clarified that vanadium trimers are randomly aligned along the c-axis direction in LiVO2, while the long-range ordering of vanadium trimers along the c-axis direction appears in LiVS2. Our results solve the longstanding issue of cluster patterns in LiVO2 and provide an experimental basis for identifying the mechanism of trimer formation.
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Submitted 3 October, 2019;
originally announced October 2019.
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Multiscale phonon blocking in Si phononic crystal nanostructures
Authors:
M. Nomura,
Y. Kage,
J. Nakagawa,
T. Hori,
J. Maire J. Shiomi,
D. Moser,
O. Paul
Abstract:
In-plane thermal conduction and phonon transport in both single-crystalline and polycrystalline Si two-dimensional phononic crystal (PnC) nanostructures were investigated at room temperature. The impact of phononic patterning on thermal conductivity was larger in polycrystalline Si PnCs than in single-crystalline Si PnCs. The difference in the impact is attributed to the difference in the thermal…
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In-plane thermal conduction and phonon transport in both single-crystalline and polycrystalline Si two-dimensional phononic crystal (PnC) nanostructures were investigated at room temperature. The impact of phononic patterning on thermal conductivity was larger in polycrystalline Si PnCs than in single-crystalline Si PnCs. The difference in the impact is attributed to the difference in the thermal phonon mean free path (MFP) distribution induced by grain boundary scattering in the two materials. Grain size analysis and numerical simulation using the Monte Carlo technique indicate that grain boundaries and phononic patterning are efficient phonon scattering mechanisms for different MFP length scales. This multiscale phonon blocking structure covers a large part of the broad distribution of thermal phonon MFPs and thus efficiently reduces thermal conduction.
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Submitted 10 February, 2015;
originally announced February 2015.
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Comment on 'A new method to calculate the spin-glass order parameter of the two-dimensional $\pm J$ Ising model'
Authors:
T. Shirakura,
F. Matsubara,
M. Shiomi
Abstract:
Contrary to the suggestion of Kitatani and Sinada (2000 J. Phys. A: Math. Gen. {\bf 33} 3545-3553), the scaling analysis of the order parameter distributions suggests the existence of a finite-temperature spin-glass phase transition $T_c\ne 0$, even if the corrections to scaling are taken into account.
Contrary to the suggestion of Kitatani and Sinada (2000 J. Phys. A: Math. Gen. {\bf 33} 3545-3553), the scaling analysis of the order parameter distributions suggests the existence of a finite-temperature spin-glass phase transition $T_c\ne 0$, even if the corrections to scaling are taken into account.
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Submitted 14 November, 2000;
originally announced November 2000.