High-Tc Superconductivity
Superconductivity above the boiling point of liquid nitrogen
First published: J. G. Bednorz & K. A. Müller, "Possible high-Tc superconductivity in the Ba-La-Cu-O system", *Zeitschrift für Physik B* 64 (1986): 189–193.
A copper-oxide ceramic superconducts at 35 K — and within a year, 92 K, above liquid nitrogen. Decades-old theoretical limits are shattered.
Bednorz and Müller at IBM Zurich discovered superconductivity at 35 K in a La-Ba-Cu-O ceramic — much higher than any previously known. Within a year, related cuprate compounds were found to superconduct above 90 K, dramatically above liquid-nitrogen temperature (77 K). The phenomenon defies the BCS theory of conventional superconductivity, requiring electron pairing mechanisms still imperfectly understood four decades later. The 1987 Nobel Prize recognised the discovery just one year after publication — the fastest such recognition in modern physics. High-Tc remains an active research field, and "room-temperature superconductivity" is one of the great unsolved goals of condensed matter physics.
Formulation
Synthesise La-Ba-Cu-O ceramic; measure resistance vs temperature. Observed: zero resistance below T_c ≈ 35 K; Meissner effect confirms superconductivity. Subsequently (Chu, Wu et al.): YBa₂Cu₃O₇ superconducting at T_c ≈ 92 K. Mechanism: not BCS-phonon-mediated; under active investigation.
Dimensions Engaged
Matter
A new macroscopic quantum state of matter, with electronic correlations not captured by standard theory.
Energy
Dissipationless current carries enormous practical and theoretical interest for energy applications.
Responses — How Schools Engage
Affirms / takes the bait 5
A canonical empirical surprise: a longstanding theoretical bound (BCS T_c limits) is shattered by an unexpected material class. Condensed matter physics restructured.
The superconducting state of cuprates is real, exotic, and resistant to standard theoretical understanding.
A new class of emergent electronic order; the structural physics of strongly-correlated electron systems remains an active research frontier.
A clean illustration of emergent collective phenomena: bulk superconductivity arises from a process of electronic organisation that resists reduction to microscopic component states.
A macroscopic quantum phenomenon with no classical analogue; the wavefunction's phase coherence persists at unprecedented temperatures.
Holds it inconclusive 1
A live empirical and theoretical question: the mechanism of high-Tc superconductivity is unresolved despite decades of intensive work.
Related Experiments
Experiments engaged by an overlapping set of schools — likely to surface the same fault lines.
Further reading
- Bednorz & Müller (1986), op. cit.
- Anderson, *The Theory of Superconductivity in the High-Tc Cuprates* (1997)
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