Abstract Body

The misfit layered compound (BiSe)_1.10(NbSe₂)_m is a superconductor with a crystal structure in which an insulating BiSe layer and superconducting NbSe₂ layers are alternately stacked via van der Waals forces. The superconducting transition temperature (T_c) varies depending on the number of superconducting layers (m). Additionally, superconductivity has anisotropy in the upper critical field (μ₀H_c2) along the in-plane crystal axes. The μ₀H_c2 along the a-axis limits by the Pauli limit, while the b-axis exceeds the Pauli Limit [1]. Furthermore, the T_c is 3 - 4 K, which is lower than 7 K for NbSe₂. The origin of the difference in the T_c is not known so far. One of the possibilities is the difference in the carrier concentration. Therefore, tuning of the carrier concentration may increase the T_c.

In this study, we investigated the Ag substitution effect for the Bi site for the superconducting properties of single-crystal samples in (BiSe)_1.10(NbSe₂)_m. These single crystals were grown using the flux method. As a result, we successfully grew single crystals with dimensions of 0.5² to 1.5² mm²(Fig.1). The obtained samples were evaluated by the X-ray diffraction (XRD) measurement, elemental composition analysis measurement by using Scanning Electron Microscope – Energy Dispersive X-ray spectrometry (SEM-EDX) and temperature and magnetic field dependent resistivity measurements. The XRD measurements indicated that the single crystals of (BiSe)_1.10(NbSe₂)_m were obtained, and m was changed with increasing Ag substitution. In this presentation, we will discuss the change in physical properties in (BiSe)_1.10(NbSe₂)_m by the Ag substitution.

References

[1] S. Matsuzawa et al., J. Phys. Conf. Ser. 2545 012002 (2023).

Figure 1. Optical image of (Bi1-xAgxSe)1.10(NbSe2)m single crystal (xAg = 0.3).

Keywords: Misfit compound, Element substitution, Superconductivity