Pressure-induced evolution of superconductivity and structural stability in a bulk 4Hb-TaSeS heterostructure

Transition-metal dichalcogenides (TMDs) are characterized by their unique layered structures and diverse electronic properties. Recent studies have highlighted the distinctive superconducting and charge density wave (CDW) behaviors of 4Hb-TaS2 and 4Hb-TaSe2. To explore the intriguing characteristics of these structurally modulated compounds, we synthesized 4Hb-TaSeS, which alternates between 1H and 1T layers, and investigated its structural and superconducting properties. At ambient pressure, 4Hb-TaSeS displays superconductivity with a transition temperature (Tc) of approximately 3.8 K. Under increasing pressure, Tc decreases to a minimum of around 2.3 K at 37 GPa, followed by a gradual recovery that forms an unusual valley in the Tc-pressure curve. High-pressure synchrotron x-ray diffraction measurements show that 4Hb-TaSeS maintains its hexagonal symmetry up to 82 GPa without undergoing any structural transitions. Resistivity measurements also indicate a transition from non-Fermi liquid to Fermi liquid behavior induced by pressure. Further theoretical calculations shed light on the pressure-dependent superconducting mechanism, demonstrating that superconductivity is primarily influenced by Ta atoms, with contributions predominantly from H-layer Ta at lower pressures, gradually shifting to T-layer Ta as pressure increases. These findings offer valuable insights into pressure-induced superconductivity in TMDs and other complex layered systems.