Faculty Profiles - YAMAKAWA Youichi

Papers - YAMAKAWA Youichi

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Drastic magnetic-field-induced chiral current order and emergent current-bond-field interplay in kagome metals Reviewed International journal

Rina Tazai, Youichi Yamakawa, Hiroshi Kontani

Proceedings of the National Academy of Sciences USA Vol. 121 ( 3 ) page： e2303476121-1 - e2303476121-10 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the National Academy of Sciences

In kagome metals, the chiral current order parameter
η with time-reversal-symmetry-breaking is the source of various exotic electronic states, while the method of controlling the current order and its interplay with the star-of-David bond order ϕ are still unsolved. Here, we reveal that tiny uniform orbital magnetization Morb[η,ϕ] is induced by the chiral current order, and its magnitude is prominently enlarged under the presence of the bond order. Importantly, we derive the magnetic-field (hz)-induced Ginzburg–Landau (GL) free energy expression ΔF[hz,η,ϕ]∝−hzMorb[η,ϕ], which enables us to elucidate the field-induced current-bond phase transitions in kagome metals. The emergent current-bond-
hz trilinear coupling term in the free energy, −m1hzη·ϕ, naturally explains the characteristic magnetic-field sensitive electronic states in kagome metals, such as the field-induced current order and the strong interplay between the bond and current orders. The GL coefficients of ΔF[hz,η,ϕ] derived from the realistic multiorbital model are appropriate to explain various experiments. Furthermore, we discuss the field-induced loop current orders in the square lattice models that have been studied in cuprate superconductors.

DOI： 10.1073/pnas.2303476121

Charge-loop current order and Z3 nematicity mediated by bond order fluctuations in kagome metals Reviewed International journal

Rina Tazai, Youichi Yamakawa, Hiroshi Kontani

Nature Communications Vol. 14 page： 7845-1 - 7845-9 2023.11

Language：English Publishing type：Research paper (scientific journal)

Recent experiments on geometrically frustrated kagome metal AV3Sb5 (A = K, Rb, Cs) have revealed the emergence of the charge loop current (cLC) order near the bond order (BO) phase. However, the origin of the cLC and its interplay with other phases have been uncovered. Here, we propose a novel mechanism of the cLC state, by focusing on the BO phase common in kagome metals. The BO fluctuations in kagome metals, which emerges due to the Coulomb interaction and the electron-phonon coupling, mediate the odd-parity particle-hole condensation that gives rise to the topological current order. Furthermore, the predicted cLC+BO phase gives rise to the Z3-nematic state in addition to the giant anomalous Hall effect. The present theory predicts the close relationship between the cLC, the BO, and the nematicity, which is significant to understand the cascade of quantum electron states in kagome metals. The present scenario provides a natural understanding.

DOI： 10.1038/s41467-023-42952-6

Mechanism of exotic density-wave and beyond-Migdal unconventional superconductivity in kagome metal AV(3)Sb(5) (A = K, Rb, Cs) Reviewed International journal

Tazai Rina, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

SCIENCE ADVANCES Vol. 8 ( 13 ) page： eabl4108-1 - eabl4108-9 2022.4

Odd-parity spin-loop-current order mediated by transverse spin fluctuations in cuprates and related electron systems Reviewed International journal

H. Kontani, Y. Yamakawa, R. Tazai, and S. Onari

Physical Review Research Vol. 3 ( 1 ) page： 013127-1 - 013127-13 2021.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher： American Physical Society

Unconventional symmetry-breaking phenomena due to nontrivial order parameters attract increasing attention in strongly correlated electron systems. Here, we predict theoretically the occurrence of nanoscale spontaneous spin current, called the spin-loop-current (sLC) order, as a promising origin of the pseudogap and electronic nematicity in cuprates. We reveal that the sLC is driven by the odd-parity electron-hole condensations that are mediated by transverse spin fluctuations around the pseudogap temperature T∗. At the same temperature, odd-parity magnon pair condensation occurs. The sLC order is “hidden” in that neither internal magnetic field nor charge-density modulation is induced, whereas the predicted sLC with finite wave-number naturally gives the Fermi arc structure. In addition, the fluctuations of sLC order work as attractive pairing interaction between adjacent hot spots, which enlarges the d-wave superconducting transition temperature Tc. The sLC state will be a key ingredient in understanding the pseudogap, electronic nematicity, as well as superconductivity in cuprates and other strongly correlated metals.

DOI： 10.1103/PhysRevResearch.3.013127

Web of Science

Nematicity and Magnetism in FeSe and Other Families of Fe-Based Superconductors Reviewed International journal

Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW X Vol. 6 ( 2 ) page： 021032-1 - 021032-15 2016.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Nematicity and magnetism are two key features in Fe-based superconductors, and their interplay is one of the most important unsolved problems. In FeSe, the magnetic order is absent below the structural transition temperature Tstr=90 K, in stark contrast to the fact that the magnetism emerges slightly below Tstr in other families. To understand such amazing material dependence, we investigate the spin-fluctuation-mediated orbital order (nxz≠nyz) by focusing on the orbital-spin interplay driven by the strong-coupling effect, called the vertex correction. This orbital-spin interplay is very strong in FeSe because of the small ratio between the Hund’s and Coulomb interactions (J¯/U¯) and large dxz, dyz-orbital weight at the Fermi level. For this reason, in the FeSe model, the orbital order is established irrespective of the fact that the spin fluctuations are very weak, so the magnetism is absent below Tstr. In contrast, in the LaFeAsO model, the magnetic order appears just below Tstr both experimentally and theoretically. Thus, the orbital-spin interplay due to the vertex correction is the key ingredient in understanding the rich phase diagram with nematicity and magnetism in Fe-based superconductors in a unified way.

DOI： 10.1103/PhysRevX.6.021032

Web of Science

Sign-Reversing Orbital Polarization in the Nematic Phase of FeSe due to the C-2 Symmetry Breaking in the Self-Energy Reviewed

Onari Seiichiro, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW LETTERS Vol. 116 ( 22 ) page： 227001-1 - 227001-6 2016.6

Odd-parity bond order and induced nonreciprocal transport in the kagome metal CsTi3Bi5 driven by quantum interference Reviewed International journal

J. Huang, Y. Yamakawa, R. Tazai, T. Morimoto, and H. Kontani

Physical Review B Vol. 111 page： 125153-1 - 125153-13 2025.3

Giant impurity effects on charge loop current order states in kagome metals Reviewed

S. Nakazawa, R. Tazai, Y. Yamakawa, S. Onari, and H. Kontani

Physical Review B Vol. 111 page： 075161-1 - 075161-10 2025.2

Real-Space Loop Current Pattern in Time-Reversal-Symmetry Breaking Phase in Kagome Metals Reviewed

Shimura, K; Tazai, R; Yamakawa, Y; Onari, S; Kontani, H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 93 ( 3 ) page： 033704-1 - 033704-5 2024.3

Superconductivity in Ternary Zirconium Telluride Zr6MTe2 with 3d Transition Metals Reviewed

Matsumoto, H; Yamakawa, Y; Okuma, R; Nishio-Hamane, D; Okamoto, Y

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 93 ( 2 ) page： 023705-1 - 023705-5 2024.2

Superconductivity in Ternary Germanide ScPdGe and Silicide ScPdSi Reviewed

Shinoda, Y; Okamoto, Y; Yamakawa, Y; Takatsu, H; Kageyama, H; Hirai, D; Takenaka, K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 93 ( 2 ) page： 023701-1 - 023701-4 2024.2

Low temperature phase transitions inside the CDW phase in the kagome metals AV3Sb5 (A=Cs, Rb, K): Significance of mixed-type Fermi surface electron correlations Reviewed

Jianxin Huang, Rian Tazai, Youichi Yamakawa, Seiichiro Onari, and Hiroshi Kontani

Physical Review B Vol. 109 ( 4 ) page： L041110-1 - L041110-6 2024.1

Superconductivity in Ternary Scandium Telluride Sc6MTe2 with 3d, 4d, and 5d Transition Metals Reviewed

Shinoda, Y; Okamoto, Y; Yamakawa, Y; Matsumoto, H; Hirai, D; Takenaka, K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 92 ( 10 ) page： 103701-1 - 103701-5 2023.8

Rigorous formalism for unconventional symmetry breaking in Fermi liquid theory and its application to nematicity in FeSe

Tazai Rina, Matsubara Shun, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 107 ( 3 ) 2023.1

Correlation-driven electronic nematicity in the Dirac semimetal BaNiS2 Reviewed

C. J. Butler, Y. Kohsaka, Y. Yamakawa, M. S. Bahramy, S. Onari, H. Kontani, T. Hanaguri, and S. Shamoto

Proceedings of the National Academy of Sciences Vol. 119 ( 49 ) page： e2212730119-1 - e2212730119-8 2022.12

d- and p-wave Quantum Liquid Crystal Orders in Cuprate Superconductors, Kappa-(BEDT-TTF)(2)X, and Coupled Chain Hubbard Models: Functional-renormalization-group Analysis

Tazai Rina, Yamakawa Youichi, Tsuchiizu Masahisa, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 90 ( 11 ) 2021.11

Unconventional orbital charge density wave mechanism in the transition metal dichalcogenide 1T-TaS2 Reviewed

Hirata Toru, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

Physical Review Research Vol. 3 ( 3 ) page： L032053-1 - L032053-6 2021.8

Pressure-induced reconstitution of Fermi surfaces and spin fluctuations in S-substituted FeSe

Kuwayama T., Matsuura K., Gouchi J., Yamakawa Y., Mizukami Y., Kasahara S., Matsuda Y., Shibauchi T., Kontani H., Uwatoko Y., Fujiwara N.

SCIENTIFIC REPORTS Vol. 11 ( 1 ) 2021.8

Unconventional Density Waves and Superconductivities in Fe-Based Superconductors and Other Strongly Correlated Electron Systems Invited Reviewed

H. Kontani, R. Tazai, Y. Yamakawa, and S. Onari

Advances in Physics Vol. 70 ( 3 ) page： 355 - 443 2021.7

Development of Spin Fluctuations under the Presence of d-wave Bond Order in Cuprate Superconductors Reviewed

Ando Satoshi, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

Journal of the Physical Society of Japan Vol. 90 ( 6 ) page： 063704-1 - 063704-5 2021.6

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Papers - YAMAKAWA Youichi