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TT: Fachverband Tiefe Temperaturen

TT 93: Superconductivity – Poster II

TT 93.11: Poster

Donnerstag, 12. März 2026, 18:00–20:00, P4

Pressure-driven evolution of upper critical field and Fermi-surface reconstruction in strong-coupling superconductor Ti₄Ir₂O — •Lifen Shi¹, Bosen Wang^2,3, and Jinguang Cheng^2,3 — ¹Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany — ²Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China — ³School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China

We report on pressure-driven evolution of the superconducting transition temperature (T_c) and upper critical field B_c2(0) of strong-coupling superconductor Ti₄Ir₂O that possesses an unusually large B_c2(0) at ambient pressure (AP). Our results reveal an extremely low-pressure coefficients of T_c, i.e. dT_c/dP = -0.047 K/GPa for P < 15 GPa and -0.017 K/GPa for 15 < P < 50 GPa, presumably associated with an inherent large bulk modulus of  252 GPa. Interestingly, we find that its Bc2(0) undergoes a smooth crossover at 35.6 GPa from well beyond to less than the Pauli paramagnetic limit BpBCS(0) = 1.84Tc; i.e., the B_c2(0) = 18.2 T = 1.7 B_pBCS(0) at AP decreases to  5.8 T = 0.88 B_pBCS(0) at 50 GPa. The density functional calculations predicted the possible occurrence of pressure-induced Fermi-surface reconstruction for the energy bands near the K point with strong spin-orbit coupling in 31-41 GPa. The present work sheds more light on this intriguing superconductor capable of resisting to large external compression and strong magnetic fields.

Keywords: superconductivity; high pressure; upper critical field; Ti4Ir2O