The pressure-induced high-Tc phase of an iron-chalcogenide superconductor has a large Fermi surface, unaltered effected masses and ununsual scattering. We have performed detailed transport studies on tetragonal Fermi surfaces of FeSe1-xSx both in Oxford and in the hybrid magnet up to 45T at the NHMFL in Tallahassee using piston cylinder pressure cell. The quantum oscillations access the Fermi surface areas and the experimental models are compared with theoretical models to understand the observed evolution. Under applied pressure, the quasi-two-dimensional multi-band Fermi surface expands and the effective masses remain large, whereas the superconductivity displays a threefold enhancement. Comparing with chemical pressure tuning of FeSe1−xSx, the Fermi surface expands in a similar manner but the effective masses and Tc are suppressed.
This work was published in npj Quantum Materials volume 9, Article number: 52 (2024).