We analyze superconductivity in a multi-orbital fermionic system near the onset of a nematic order, using doped FeSe as an example. We associate nematicity with spontaneous polarization between d_xz and d_yz orbitals. We derive pairing interaction, mediated by soft nematic fluctuations, and show that it is attractive, and its strength depends on the position on the Fermi surface. As the consequence, right at the nematic quantum-critical point (QCP), superconducting gap opens up at T_c only at special points and extends into finite arcs at T < T_c. In between the arcs the Fermi surface remains intact. This leads to highly unconventional behavior of the specific heat, with no jump at T_c and seemingly finite offset at T = 0. We discuss gap structure and pairing symmetry away from a QCP and compare nematic and spin-fluctuation scenarios. We apply the results to FeSe_1−xS_x and FeSe_1−xTe_x.

我们以掺杂 FeSe 为例，分析了向列序开始附近的多轨道费米子系统中的超导性。我们将向列性与d _xz和d _yz轨道之间的自发极化联系起来。我们推导了由软向列波动介导的配对相互作用，并表明它具有吸引力，并且其强度取决于费米表面上的位置。因此，就在向列量子临界点 (QCP)，超导能隙仅在特殊点处的T _c处打开，并延伸到T  <  T _c处的有限弧。在弧线之间，费米面保持完整。这导致比热的非常规行为，在T _{c处没有跳跃，并且在}T = 0处看似有限的偏移 。我们讨论远离 QCP 的间隙结构和配对对称性，并比较向列和自旋涨落场景。我们将结果应用于 FeSe _{1− x} S _x和 FeSe _{1− x} Te _x。