Superconductivity-Driven Unipolar State in a Superatomic Antipolar Metal

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Abstract
Coexistence of electric polarization with metallicity or superconductivity defines the exotic polar metallic or superconducting states, which are exceedingly rare due to inherent mutual exclusivity. Recently, interweaved charge-density-wave (CDW) and antipolar charge orders have been discovered in a metallic superatomic crystal Au 6 Te 12 Se 8 (ATS). However, their interplay and competition with the emergent superconducting state remains elusive. Here, we report experimental investigations on the superconducting state, interacting with pre-existing CDW and antipolar metal in ATS crystals, using STM/STS. We clearly identify the distinct temperatures for Cooper pair preformation (9.9 K) and subsequent superconducting condensation (2.8 K). Our results reveal that the preformed Cooper pairs gradually suppress the existing CDW upon cooling. Moreover, the antipolar charge distribution is converted into a ferrielectric-like unipolar state by superconductivity below the superconducting transition. These findings establish ATS as a unique host for an exotic charge-polarized superconducting state, providing a promising platform for exploring novel polar-superconductivity interactions.

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