Zeeman effect on topological surface states of UTe₂

Odd-parity superconductors are expected to host topological surface states protected by particle–hole symmetry in time-reversal-invariant phases. UTe₂, a leading candidate for unconventional spin-triplet pairing, provides a promising platform to realize such low-energy surface excitations. Compared with the CVT-grown crystal (T_c=1.6 K), MSF-grown sample (T_c=2.1 K) exhibits a comparable residual density of states (DOS) at sub-gap energy despite the enhanced T_c. Given its much smaller residual-resistivity ratio, the residual DOS is unlikely to arise from disorder but is rather intrinsic to the electronic structure of UTe₂. Using a vector magnetic-field STM, we investigate the response of the site-resolved superconducting gap to magnetic fields applied along different axes. A pronounced field-induced deepening of the superconducting gap is observed, highlighting a μeV-scale Zeeman effect associated with the topological surface states. These results demonstrate the topological origin of the surface states and elucidating their spatial distribution, offering microscopic insight into the interplay between spin-triplet superconductivity and topology in UTe₂.