掲載種別：研究論文（学術雑誌）   出版者・発行元：American Physical Society (APS)  

DOI： 10.1103/physrevresearch.3.l032071

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.3.L032071/fulltext

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Society of Japan  

We report the magnetic susceptibility and the magnetization under pressures up to 1.7 GPa above the critical pressure, P-c similar to 1.5 GPa, for H parallel to a, b, and c-axes in the novel spin triplet superconductor UTe2. The anisotropic magnetic susceptibility at low pressure with the easy magnetization a-axis changes to the quasi-isotropic behavior at high pressure, revealing a rapid suppression of the susceptibility for a-axis, and a gradual increase of the susceptibility for the b-axis. At 1.7 GPa above P-c, magnetic anomalies are detected at T-MO similar to 3K and T-WMO similar to 10 K. The former anomaly corresponds to long-range magnetic order, most likely antiferromagnetism, while the latter shows a broad anomaly, which is probably due to the development of short range order. The unusual decrease and increase of the susceptibility below T-WMO for H parallel to a and b-axes, respectively, indicate the complex magnetic properties at low temperatures above P-c. This is related to the interplay between multiple fluctuations dominated by antiferromagnetism, ferromagnetism, valence and Fermi surface instabilities.

DOI： 10.7566/jpsj.90.073703

Web of Science

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Physical Society (APS)  

DOI： 10.1103/physrevb.103.245114

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.103.245114/fulltext

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Physical Society (APS)  

DOI： 10.1103/physrevb.103.094504

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.103.094504/fulltext

掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

DOI： 10.1038/s41586-020-2590-4

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掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.30.011043

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Physical Society (APS)  

DOI： 10.1103/physrevlett.123.217001

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.123.217001/fulltext

記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.74.2.0_1867

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Physical Society (APS)  

DOI： 10.1103/physrevb.98.224510

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.98.224510/fulltext

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Society of Japan  

DOI： 10.7566/jpsj.87.014705

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記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.73.2.0_1738

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記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.73.1.0_2034

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Physical Society of Japan  

The five-orbital Hubbard model for iron-based superconductors is investigated by using the dynamical mean-field theory combined with the Eliashberg equation to clarify the local correlation effects on the electronic states and the superconductivity. In the specific case where the antiferromagnetic (AMF) and the antiferro-orbital (AFO) fluctuations are comparably enhanced, the orbital dependence of the vertex function becomes significantly large while that of the self-energy is small, in contrast to the AFM fluctuation-dominated case where the vertex function (the self-energy) shows small (large) orbital dependence. The orbital-dependent vertex function together with the nesting between the inner and outer hole Fermi surfaces results in the enhancement of the inter-orbital ferromagnetic (FM) fluctuation in addition to the AFM and AFO fluctuations. In this case, the hole-s_±-wave pairing with the sign change of the two hole Fermi surfaces is mediated by the coexisting three fluctuations as expected to be observed in a specific compound LiFeAs.

DOI： 10.7566/jpsj.85.114709

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP Publishing  

The five-orbital Hubbard model for iron pnictides is investigated by using the dynamical meanfield theory (DMFT) in conjunction with the Eliashberg equation in the strong correlation regime where the ferromagnetic (FM) and antiferromagnetic (AFM) fluctuations are simultaneously enhanced. When the intraorbital Coulomb interaction is a little smaller than the interorbital one, the FM fluctuation is largely enhanced due to the significant orbital dependence of the vertex correction and becomes comparable to the AFM fluctuation, in contrast to the result from the random phase approximation where the AFM fluctuation is exclusively enhanced due to the nesting between hole and electron Fermi surfaces (FSs). The enhanced FM fluctuation induces the large repulsive pairing interaction between inner and outer hole FSs while the AFM fluctuation does between the hole and electron FSs. The latter is partially counteracted by the attractive pairing interaction mediated by the antiferro-orbital fluctuation. The resulting pairing state is found to be a novel s-wave in which the gap function of the inner hole FS has the opposite sign to that of the outer hole and electron FSs.

DOI： 10.1088/1742-6596/592/1/012077

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その他リンク： http://stacks.iop.org/1742-6596/592/i=1/a=012077?key=crossref.2245a071b21865554ab6a5612ddb1599

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：The Physical Society of Japan  

We investigate the electronic state and the superconductivity in the 5-orbital Hubbard model for iron pnictides by using the dynamical mean-field theory together with the linearized Eliashberg equation. The renormalization factor exhibits a significant orbital dependence resulting in the band-dependence of the mass enhancement. The critical interactions towards the magnetic, orbital and superconducting instabilities are calculated and found to be suppressed as compared to the corresponding RPA results due to the correlation effects. Remarkably, the s_<++>-pairing phase due to the orbital fluctuation is expanded as compared to the RPA result, while the s_±-pairing phase due to the magnetic fluctuation is largely reduced.

DOI： 10.7566/jpscp.3.015020

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Physical Society of Japan  

The electronic states and superconductivity in iron pnictides are studied on the basis of the 16 band d-p model which includes both the onsite Coulomb interaction between Fe d electrons and the intersite one between Fe d and pnictogen p electrons. The model well accounts for experimentally observed two fluctuations: the d-d interaction-enhanced antiferromagnetic (AFM) fluctuation and the d-p interaction-enhanced ferro-orbital (FO) fluctuation responsible for the C_<66> elastic softening. The AFM fluctuation induces the repulsive pairing interaction for q ～ Q_<AF> while the FO does the attractive one for q ～ 0 resulting in the s_±-wave superconductivity where the two fluctuations cooperatively enhance the superconducting transition temperature T_c without any competition by virtue of the q-space segregation.

DOI： 10.7566/jpsj.83.043704

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Physical Society of Japan  

We investigate a two-orbital model for iron-based superconductors to elucidate the effect of interplay between electron correlation and Jahn-Teller electron-phonon coupling by using the dynamical mean-field theory combined with the exact diagonalization method. When the intra- and inter-orbital Coulomb interactions, U and U′, increase with U = U′, both the local spin and orbital susceptibilities, χ_s and χ_o, increase with χ_s = χ_o in the absence of the Hund's rule coupling J and the electron-phonon coupling g. In the presence of J and g, there are distinct two regimes: for J >__～ 2g^2 /ω_0 with the phonon frequency ω_0, χ_s is enhanced relative to χ_o and shows a divergence at J = J_c above which the system becomes Mott insulator, while for J <__～ 2g^2/ω_0, χ_o is enhanced relative to χ_s and shows a divergence at g = g_c above which the system becomes bipolaronic insulator. In the former regime, the superconductivity is mediated by antiferromagnetic fluctuations enhanced due to Fermi-surface nesting and is found to be largely dependent on carrier doping. On the other hand, in the latter regime, the superconductivity is mediated by ferro-orbital fluctuations and is observed for wide doping region including heavily doped case without the Fermi-surface nesting.

DOI： 10.7566/jpsj.83.044711

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Physical Society of Japan  

We investigate the electronic state and the superconductivity in the five-orbital Hubbard model for iron pnictides by using the dynamical mean-field theory in conjunction with the Eliashberg equation. The renormalization factor exhibits significant orbital dependence resulting in the large change in the band dispersion as observed in recent ARPES experiments. The critical interactions towards the magnetic, orbital and superconducting instabilities are suppressed as compared with those from the random phase approximation (RPA) due to local correlation effects. Remarkably, the s_{++}-pairing phase due to the orbital fluctuation is largely expanded relative to the RPA result, while the s_{\pm}-pairing phase due to the magnetic fluctuation is reduced.

DOI： 10.7566/jpsj.82.123712

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