Superconducting gap evolution of kagome metal CsV 3 Sb 5 under pressure

Kagome superconductors AV 3 Sb 5 (A=Cs, V, Sb) have served as an ideal platform to unveil the intriguing competitions between charge-density-wave (CDW), superconductivity and possible nontrivial topological states. We report soft point-contact spectroscopy (SPCS) studies on CsV 3 Sb 5 under pressure up to 2.5 GPa. Its superconducting transition temperature T c and gaps for SPCS at pressure P = 0.1 GPa suggest the absence of the adverse local strain effect as observed in point-contacts at ambient pressure, while the SPCS-determined T c under hydrostatic pressure deviates from the reported double dome feature below 2.5 GPa. Three distinct gap values in CsV 3 Sb 5 are proposed to exist through the whole pressure range with 2Δ 1 / k B T c ≤1, 2Δ 2 /k B T c ∼2.3 -3.0 and 2Δ 3 / k B T c >3.5. The two smaller gaps for 2Δ 1 / k B T c ≤1 and 2Δ 2 / k B T c ∼2.3–3.0 are robust under pressure, while there is no trace of the largest gap 2Δ 3 / k B T c >3.5 for SPCS in the c direction with P ≤ P 1 = 0.7 GPa and P ≥ P 2 = 2.0 GPa and it becomes observable in the pressure range of ( P 1 , P 2 ), suggesting a complex relation between CDW and superconductivity between ( P 1 , P 2 ).