STRAIN ENGINEERING TUNING OF TOPOLOGICAL SUPERCONDUCTIVITY AND UNCONVENTIONAL PAIRING SYMMETRY: FROM SR₂RUO₄ TO DOPED BI₂SE₃

The pairing mechanism and topological properties of unconventional superconductors are frontier hotspots in condensed matter physics. As a clean tuning means, strain engineering can continuously adjust lattice constants, band structures and electron correlation strength without introducing chemical disorder, thereby providing an ideal platform for exploring the evolution of superconducting phase diagrams and pairing symmetry. This article systematically reviews the latest theoretical and experimental progress of strain engineering in tuning two representative unconventional superconductors — the chiral p-wave candidate Sr₂RuO₄ and the nematic topological superconductor doped Bi₂Se₃. First, we review the basic theoretical framework of strain engineering, including the modulation mechanism of lattice strain on band topology, and the applications of the functional renormalization group (FRG) and self-consistent mean-field renormalization group (SMFRG) methods in the analysis of competing interactions. Second, we focus on the evolution of the superconducting phase diagram of Sr₂RuO₄ under uniaxial and biaxial strain, particularly the strain-induced p-wave to s-wave superconducting transition and the enhancement effect of the Van Hove Singularity on the critical temperature. Then, we analyze the tuning role of strain on the nematic order and odd-parity spin-triplet pairing of doped Bi₂Se₃. Finally, we give an outlook on the application prospects of strain engineering in topological heterostructure interface superconductivity and the construction of Majorana zero modes (MZMs).