Superconducting gap evolution of kagome metal CsV3Sb5 under pressure

Kagome superconductors AV3Sb5 (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 CsV3Sb5 under pressure up to 2.5 GPa. Its superconducting transition temperature Tc 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 Tc under hydrostatic pressure deviates from the reported double dome feature below 2.5 GPa. Three distinct gap values in CsV3Sb5 are proposed to exist through the whole pressure range with 2Δ1/kBTc≤1, 2Δ2/kBTc∼2.3 -3.0 and 2Δ3/kBTc>3.5. The two smaller gaps for 2Δ1/kBTc≤1 and 2Δ2/kBTc∼2.3–3.0 are robust under pressure, while there is no trace of the largest gap 2Δ3/kBTc>3.5 for SPCS in the c direction with P ≤ P1 = 0.7 GPa and P ≥ P2 = 2.0 GPa and it becomes observable in the pressure range of (P1, P2), suggesting a complex relation between CDW and superconductivity between (P1, P2).