标题： 高压 Kagome 金属 CsV$_3$Sb$_5$中具有旋转对称性破缺的完全能隙超导性 显示英文标题

标题： Fully-gapped superconductivity with rotational symmetry breaking in pressurized kagome metal CsV$_3$Sb$_5$

摘要： Kagome金属CsV$_3$Sb$_5$的发现引起了对其复杂物理性质的极大兴趣，尤其是其在不同压力下的超导行为，尽管其本质仍存在争议。 在此，我们进行了低温高压$^{121/123}$Sb核四极共振（NQR）测量，以探索CsV$_3$Sb$_5$中的超导配对对称性。 在环境压力下，我们发现自旋晶格弛豫率 1/$T_1$在超导态内的 $T \sim$ 0.4 $T_\textrm{c}$ 处出现拐点，并且随着温度进一步降低遵循 $T^3$ 变化。 这表明存在两个超导能隙，在较小的能隙中有线节点。 As pressure increases beyond $P_{\rm c} \sim 1.85$ GPa, where the charge-density wave phase is completely suppressed, 1/$T_1$ shows no Hebel-Slichter peak just below $T_\textrm{c}$, and decreases rapidly, even faster than $T^5$, indicating that the gap is fully opened for pressures above $P_{\rm c}$. In this high pressure region, the angular dependence of the in-plane upper critical magnetic field $H_{\rm c2}$ breaks the $C_6$ rotational symmetry. 我们提出了$s+id$对于$P > P_{\rm c}$的配对，它解释了 1/$T_1$和$H_{\rm c2}$的行为。 我们的研究结果表明，CsV$_3$Sb$_5$是一种非传统超导体，并且在高压下其超导态更加奇特。 显示英文摘要

摘要： The discovery of the kagome metal CsV$_3$Sb$_5$ has generated significant interest in its complex physical properties, particularly its superconducting behavior under different pressures, though its nature remains debated. Here, we performed low-temperature, high-pressure $^{121/123}$Sb nuclear quadrupole resonance (NQR) measurements to explore the superconducting pairing symmetry in CsV$_3$Sb$_5$. At ambient pressure, we found that the spin-lattice relaxation rate 1/$T_1$ exhibits a kink at $T \sim$ 0.4 $T_\textrm{c}$ within the superconducting state and follows a $T^3$ variation as temperature further decreases. This suggests the presence of two superconducting gaps with line nodes in the smaller one. As pressure increases beyond $P_{\rm c} \sim 1.85$ GPa, where the charge-density wave phase is completely suppressed, 1/$T_1$ shows no Hebel-Slichter peak just below $T_\textrm{c}$, and decreases rapidly, even faster than $T^5$, indicating that the gap is fully opened for pressures above $P_{\rm c}$. In this high pressure region, the angular dependence of the in-plane upper critical magnetic field $H_{\rm c2}$ breaks the $C_6$ rotational symmetry. We propose the $s+id$ pairing at $P > P_{\rm c}$ which explains both the 1/$T_1$ and $H_{\rm c2}$ behaviors. Our findings indicate that CsV$_3$Sb$_5$ is an unconventional superconductor and its superconducting state is even more exotic at high pressures.