The breakdown of superconductivity in quantum materials

What causes superconductivity to disappear at Tc in quantum materials? In my talk, I will present two case studies: First, I will show how in the disordered superconductor titanium nitride, electron pairs exist far above Tc. For this study, we developed new instrumentation that can unambiguously and quantitatively detect electron pairs: the electron pair microscope [1,2]. We discovered a state above Tc that, much like an ordinary metal, has no (pseudo)gap, but appears to carry charge entirely via paired electrons. [3]. Second, I will discuss overdoped high-temperature superconductors, where we found that superconductivity breaks down because of the formation of nanometer-sized puddles in a metallic matrix. Again, superconductivity is not limited by the pairing interaction [4].

References

[1] KM Bastiaans et al., RSI 89, 093709 (2018)

[2] KM Bastiaans, D. Cho et al., Nature Physics 14, 1183 (2018)

[3] KM Bastiaans, et al. Science 374, 608 (2021)

[4] Tromp & Benschop, et al. Nature Materials (2023)

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