Inducing or enhancing superconductivity in topological materials is an important route toward topological superconductivity. Reducing the thickness of transition metal dichalcogenides (e.g. WTe 2 and MoTe 2 ) has provided an important pathway to engineer superconductivity in topological matters; for instance, emergent superconductivity with T c ∼ 0.82 K was observed in monolayer WTe 2 1, 2 which also hosts intriguing quantum spin Hall effect 3 , although the bulk crystal is nonsuperconducting. However, such monolayer sample is difficult to obtain, unstable in air, and with extremely low T c , which could pose a grand challenge for practical applications. Here we report an experimentally convenient approach to control the interlayer coupling to achieve tailored topological properties, enhanced superconductiv-1 arXiv:1911.02228v1 [cond-mat.mtrl-sci]

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We study the new details of electronic and thermoelectric properties of polycrystalline layered oxychalcogenide systems of (BiO)Cu Ch ( Ch = Se, Te) prepared by using a solid-state reaction. The systems were characterized by using photoemission (PE) spectroscopy and four-probe temperature-dependent electrical resistivity ρ( T). PE spectra are explained by calculating the electronic properties using the generalized-gradient approximation method. PE spectra and ρ( T) show that (BiO)CuSe system is a semiconductor, while (BiO)CuTe system exhibits the metallic behavior that induces the high thermoelectric performance. The calculation of electronic properties of (BiO)Cu Ch ( Ch = S, Se, Te) confirms that the metallic behavior of (BiO)CuTe system is mainly induced by Te 5p states at Fermi energy level, while the indirect bandgaps of 0.68 and 0.40 eV are obtained for (BiO)CuS and (BiO)CuSe systems, respectively. It is also shown that the local symmetry distortion at Cu site strongly stimulates Cu 3d-t to be partially hybridized with Ch p orbitals. This study presents the essential properties of the inorganic systems for novel functional device applications.

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Manipulating the strength of the interlayer coupling is an effective strategy to induce intriguing properties in layered materials. Recently, enhanced superconductivity has been reported in Weyl semimetal MoTe2 and WTe2 via ionic liquid cation intercalation. However, how the superconductivity enhancement depends on the interlayer interaction still remains elusive. Here by inserting ionic liquid cations with different sizes into MoTe2 through this strategy, we are able to tune the interlayer spacing of the intercalated MoTe2 samples and reveal the dependence of superconducting transition temperature T c on the interlayer spacing. Our results show that T c increases with the interlayer spacing, suggesting that the weakened interlayer coupling plays an important role in the superconductivity. Interestingly, the intercalation induced superconductivity shows a high Ginzburg-Landau anisotropy, which suggests a quasi-two-dimensional nature of the superconductivity where the adjacent superconducting layers are coupled through Josephson tunneling.