CsV3Sb5 is a newly discovered Z2 topological kagome metal showing the coexistence of a charge density wave (CDW)-like order at T* = 94 K and superconductivity (SC) at Tc = 2.5 K at ambient pressure. Here we study the interplay between CDW and SC in CsV3Sb5 via measurements of resistivity and magnetic susceptibility under hydrostatic pressures. We find that the CDW transition decreases with pressure and experience a subtle modification at Pc1  0.6-0.9 GPa before it vanishes completely at Pc2  2 GPa. Correspondingly, Tc(P) displays an unusual M-shaped double dome character with two maxima around Pc1 and Pc2, respectively, leading to a tripled enhancement of Tc to about 8 K at 2 GPa. The obtained temperature-pressure phase diagram resembles those of many unconventional superconductors, illustrating an intimated competition between CDW-like order and SC. The competition is found to be particularly strong for the intermediate pressure range Pc1  P  Pc2 as evidenced by the broad superconducting transition and reduced superconducting volume fraction. This work not only demonstrates the potential to raise the Tc of the V-based kagome superconductors, but also offers more insights into the rich physics related to the electronic correlations in this novel family of topological kagome metals.

We herein report the large-scale synthesis of Bi 2 Te 32x Se x (0.6 ¡ x ¡ 0.75) nanoplatelets through a hydrothermal method and subsequent spark plasma sintering. The effect of selenium alloying and the spark plasma sintering temperature on the thermoelectric properties of the Bi 2 Te 3 nanostructured bulk materials were investigated. The results indicate that compared to samples fabricated in an autoclave, preparing Bi 2 Te 32x Se x in glass beaker with suitable Se alloying and appropriate sintered temperature is an efficient way to reduce the lattice thermal conductivity due to a large number of Bi 2 TeO 5 nanodots with sizes of around 10 nm. Meanwhile, a decrease in electrical resistivity due to increase in carrier mobility and an enhancement of the Seebeck coefficient attribute to decrease in carrier concentration were observed. As a result, the thermoelectric figure-of-merit, ZT, is significantly improved and the maximum value reaches 0.96 for Bi 2 Te 2.25 Se 0.75 at 490 K.