*Article* **Ginzburg–Landau Analysis on the Physical Properties of the Kagome Superconductor CsV3Sb5**

**Tianyi Han 1, Jiantao Che 1, Chenxiao Ye <sup>2</sup> and Hai Huang 1,\***


**\*** Correspondence: huanghai@ncepu.edu.cn

**Abstract:** The kagome lattice consisting of corner-sharing triangles has been studied in the context of quantum physics for more than seventy years. For the novel discovered kagome superconductor CsV3Sb5, identifying the pairing symmetry of order parameter remained an elusive problem until now. Based on the two-band Ginzburg–Landau theory, we study the temperature dependence of upper critical field and magnetic penetration depth for this compound. All theoretical results are consistent with the experimental data, which strongly indicates the existence of two-gap *s*-wave superconductivity in this system. In addition, it is worth noting that the anisotropy of effective masses in the band with large (or small) gap is about 70 (or 2.4). With the calculation of the Kadowaki– Woods ratio as 0.58 <sup>×</sup> <sup>10</sup>−<sup>5</sup> <sup>μ</sup><sup>Ω</sup> cm mol2 K2 mJ<sup>−</sup>2, the semi-heavy-fermion feature is suggested in the compound CsV3Sb5.

**Keywords:** Ginzburg–Landau theory; two-gap *s*-wave superconductivity; CsV3Sb5; heavy fermion system
