JST・Japan Science and Technology Agency Pioneering Research Initiated by the Next Generation program

D2

134

3793

takahashi.hidemitsu.23r_at_st.kyoto-u.ac.jp

### 2022

Chuang, C-Wen; Souma, S; Moriya, A; Nakayama, K; Ikeda, A; Kawaguchi, M; Obata, K; Saha, S Ranjan; Takahashi, H; Kitagawa, S; Ishida, K; Tanaka, K; Kitamura, M; Horiba, K; Kumigashira, H; Takahashi, T; Yonezawa, S; Paglione, J; Maeno, Y; Sato, T

Fermiology of a topological line-nodal compound CaSb2 and its implication to superconductivity: Angle-resolved photoemission study Journal Article

In: Physical Review Materials, vol. 6, iss. 10, pp. 104203, 2022.

@article{CaSb2ARPES,

title = {Fermiology of a topological line-nodal compound CaSb2 and its implication to superconductivity: Angle-resolved photoemission study},

author = {C-Wen Chuang and S Souma and A Moriya and K Nakayama and A Ikeda and M Kawaguchi and K Obata and S Ranjan Saha and H Takahashi and S Kitagawa and K Ishida and K Tanaka and M Kitamura and K Horiba and H Kumigashira and T Takahashi and S Yonezawa and J Paglione and Y Maeno and T Sato},

url = {https://arxiv.org/abs/2211.15083},

doi = {10.1103/PhysRevMaterials.6.104203},

year = {2022},

date = {2022-10-24},

urldate = {2022-10-24},

journal = {Physical Review Materials},

volume = {6},

issue = {10},

pages = {104203},

abstract = {We performed angle-resolved photoemission spectroscopy with microfocused beam on a topological line-nodal compound CaSb2 which undergoes a superconducting transition at the onset Tc ∼ 1.8 K, to clarify the Fermi-surface topology relevant to the occurrence of superconductivity. We found that a three-dimensional hole pocket at the Γ point is commonly seen for two types of single-crystalline samples fabricated by different growth conditions. On the other hand, the carrier-doping level estimated from the position of the chemical potential was found to be sensitive to the sample fabrication condition. The cylindrical electron pocket at the Y(C) point predicted by the calculations is absent in one of the two samples, despite the fact that both samples commonly show superconductivity with similar Tc's. This suggests a key role of the three-dimensional hole pocket to the occurrence of superconductivity, and further points to an intriguing possibility to control the topological nature of superconductivity by carrier tuning in CaSb2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Ikeda, A; Saha, S Ranjan; Graf, D; Saraf, P; Sokratov, D Sergeevich; Hu, Y; Takahashi, H; Yamane, S; Jayaraj, A; Sławińska, J; Nardelli, M Buongiorno; Yonezawa, S; Maeno, Y; Paglione, J

Quasi-two-dimensional Fermi surface of superconducting line-nodal metal CaSb2 Journal Article

In: Physical Review B, vol. 106, iss. 7, pp. 075151, 2022.

@article{A.Ikeda_PRB_2022,

title = {Quasi-two-dimensional Fermi surface of superconducting line-nodal metal CaSb2},

author = {A Ikeda and S Ranjan Saha and D Graf and P Saraf and D Sergeevich Sokratov and Y Hu and H Takahashi and S Yamane and A Jayaraj and J Sławińska and M Buongiorno Nardelli and S Yonezawa and Y Maeno and J Paglione},

url = {https://arxiv.org/abs/2206.15346},

doi = {10.1103/PhysRevB.106.075151},

year = {2022},

date = {2022-08-29},

urldate = {2022-08-29},

journal = {Physical Review B},

volume = {106},

issue = {7},

pages = {075151},

abstract = {We report on the Fermi surfaces and superconducting parameters of CaSb2 single crystals (superconducting below Tc ∼ 1.8 K) grown by the self-flux method. The frequency of de Haas–van Alphen and Shubnikov–de Haas oscillations evidences a quasi-two-dimensional (quasi-2D) Fermi surface, consistent with one of the Fermi surfaces forming Dirac lines predicted by first-principles calculations. Measurements in the superconducting state reveal that CaSb2 is close to a type-I superconductor with the Ginzburg-Landau parameter of around unity. The temperature dependence of the upper critical field Hc2 is well described by a model considering two superconducting bands, and the enhancement of the effective mass estimated from Hc2 (0 K) is consistent with the quasi-2D band observed by the quantum oscillations. Our results indicate that a quasi-2D band forming Dirac lines contributes to the superconductivity in CaSb2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

### 2021

Takahashi, H; Kitagawa, S; Ishida, K; Kawaguchi, M; Ikeda, A; Yonezawa, S; Maeno, Y

S-Wave Superconductivity in the Dirac Line-Nodal Material CaSb2 Journal Article

In: Journal of the Physical Society of Japan, vol. 90, pp. 073702, 2021.

@article{H.Takahashi_JPSJ_2021,

title = {S-Wave Superconductivity in the Dirac Line-Nodal Material CaSb2},

author = {H Takahashi and S Kitagawa and K Ishida and M Kawaguchi and A Ikeda and S Yonezawa and Y Maeno},

url = {https://arxiv.org/abs/2105.13614},

doi = {10.7566/JPSJ.90.073702},

year = {2021},

date = {2021-06-11},

urldate = {2021-06-11},

journal = {Journal of the Physical Society of Japan},

volume = {90},

pages = {073702},

abstract = {We performed 121/123Sb-nuclear quadrupole resonance (NQR) measurements on the superconducting (SC) line-nodal material CaSb2 in order to investigate electronic properties in the normal and SC states from a microscopic point of view. In the normal state, the nuclear spin–lattice relaxation rate 1/T1 for the Sb(1) site, which is responsible for the line-nodal parts, is approximately proportional to temperature, indicating the conventional Fermi liquid state. From comparison with band structure calculations, it is considered that the NQR properties related to the line-nodal character are hidden because the conventional behavior originating from Fermi-surface parts away from the nodes is dominant. In the SC state, a clear coherence peak just below the transition temperature and an exponential decrease at lower temperatures were observed in 1/T1. These results strongly suggest that conventional s-wave superconductivity with a full gap is realized in CaSb2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

### 1996

Nakamura, F; Kodama, M; Sakita, S; Maeno, Y; Fujita, T; Takahashi, H; Môri, N

Pressure dependence of out-of-plane conduction Journal Article

In: Physical Review B - Condensed Matter and Materials Physics, vol. 54, no. 14, pp. 10061-10064, 1996.

@article{Nakamura199610061,

title = {Pressure dependence of out-of-plane conduction},

author = {F Nakamura and M Kodama and S Sakita and Y Maeno and T Fujita and H Takahashi and N Môri},

doi = {10.1103/PhysRevB.54.10061},

year = {1996},

date = {1996-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {54},

number = {14},

pages = {10061-10064},

abstract = {Pressure dependence of out-of-plane resistivity (Formula presented) has been investigated in an optimally-doped high-(Formula presented) cuprate (Formula presented)(Formula presented)(Formula presented). By applying pressure, we found a drastic decrease in (Formula presented) which reaches 50% at P=8 GPa. This surprisingly large P dependence implies that the thermal contraction along the c axis is significantly reflected in the (Formula presented)(T) curve, leading to a metal-like term; hence (Formula presented)(Formula presented)(Formula presented) is essentially characterized as a two-dimensional metal modified with nonmetallic conduction between (Formula presented) layers. Tunneling is suggested for a possible mechanism for (Formula presented). © 1996 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Nakamura, F; Kodama, M; Kikugawa, N; Sakita, S; Maeno, Y; Fujita, T; Takahashi, H; Môri, N

Pressure effects of resistivity along the c axis in La2-xSrxCuO4 Journal Article

In: Journal of Low Temperature Physics, vol. 105, no. 3-4, pp. 915-920, 1996.

@article{Nakamura1996915,

title = {Pressure effects of resistivity along the c axis in La2-xSrxCuO4},

author = {F Nakamura and M Kodama and N Kikugawa and S Sakita and Y Maeno and T Fujita and H Takahashi and N Môri},

doi = {10.1007/BF00768499},

year = {1996},

date = {1996-01-01},

journal = {Journal of Low Temperature Physics},

volume = {105},

number = {3-4},

pages = {915-920},

abstract = {Out-of-plane resistivity ρc(T) of optimally-doped high-Tc superconductor La2-xSrxCuO4 has been investigated under hydrostatic pressure up to 8GPa. We found a drastic decrease in ρc which reaches 50% at 8GPa. The large change of ρc is understood as due to a small variation of the lattice parameter c. In comparison with a change of ρc(T) estimated from a change of c due to thermal contraction, we conclude that the well known temperature-linear dependence of ρc is apparent metallic one; essentially ρc is nonmetallic over the whole temperature range, and can be described in terms of tunneling or quantum hopping conduction between CuO2 layers. Such tunneling conduction is enhanced by the scattering in the CuO2 plane at the oxygen defects which affect the in-plane resistivity only very weakly. © 1996 Plenum Publishing Corporation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}