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.

The successful synthesis of superconducting infinite-layer nickelate thin films with the highest Tc ≈ 15 K has ignited great enthusiasm for this material class as potential analogs of the high-Tc cuprates. Pursuing a higher Tc is always an imperative task in studying a new superconducting material system. Here we report high-quality Pr0.82Sr0.18NiO2 thin films with Tconset ≈ 17 K synthesized by carefully tuning the amount of CaH2 in the topotactic chemical reduction and the effect of pressure on its superconducting properties by measuring electrical resistivity under various pressures in a cubic anvil cell apparatus. We find that the onset temperature of the superconductivity, Tconset, can be enhanced monotonically from ~17 K at ambient pressure to ~31 K at 12.1 GPa without showing signatures of saturation upon increasing pressure. This encouraging result indicates that the Tc of infinite-layer nickelates superconductors still has room to go higher and it can be further boosted by applying higher pressures or strain engineering in the heterostructure films.

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We report the crystal structure, charge-density-wave (CDW), superconductivity (SC), and ferromagnetism (FM) in CuIr2-xCrxTe4 (0 ≤ x ≤ 2) chalcogenides. Powder x-ray diffraction (PXRD) results reveal that CuIr2-xCrxTe4 series are distinguished between two structural types and three different regions: (i) layered trigonal structure region, (ii) mixed phase regions, (iii) spinel structure region. Besides, Cr substitution for Ir site results in rich physical properties including the collapse of CDW, the formation of dome-shaped like SC, and the emergence of magnetism. Cr doping slightly elevates the superconducting critical temperature (Tsc) to its highest Tsc = 2.9 K around x = 0.06. As x increases from 0.3 to 0.4, the ferromagnetic Curie temperature (Tc) increases from 175 to 260 K. However, the Tc remains unchanged in the spinel range of 1.9 ≤ x ≤ 2. This finding provides a comprehensive material platform for investigating the interplay between CDW, SC, and FM multipartite quantum states.

A recent focus of quantum spin liquid (QSL) studies is how disorder/randomness in a QSL candidate affects its true magnetic ground state. The ultimate question is whether the QSL survives disorder or the disorder leads to a “spin-liquid-like” state, such as the proposed random-singlet (RS) state. Since disorder is a standard feature of most QSL candidates, this question represents a major challenge for QSL candidates. YbMgGaO4, a triangular lattice antiferromagnet with effective spin-1/2 Yb3+ions, is an ideal system to address this question, since it shows no long-range magnetic ordering with Mg/Ga site disorder. Despite the intensive study, it remains unresolved as to whether YbMgGaO4 is a QSL or in the RS state. Here, through ultralow-temperature thermal conductivity and magnetic torque measurements, plus specific heat and DC magnetization data, we observed a residual κ0/T term and series of quantum spin state transitions in the zero temperature limit for YbMgGaO4. These observations strongly suggest that a QSL state with itinerant excitations and quantum spin fluctuations survives disorder in YbMgGaO4.

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