Is the anomalous metal a true zero-temperature phase? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Is the anomalous metal a true zero-temperature phase?
Plain
Some thin superconducting films stop losing resistance on cooling and level off at a small value. The dispute is whether this is a genuine state of matter or a result of electrical noise and stray radiation that keep the electrons warmer than the thermometer.
Precise · changed · core
Revision 1: In $2\mathrm{D}$ superconducting films and arrays (amorphous InOx, MoGe, Ta, transition-metal dichalcogenide superconductors, Josephson-junction arrays) tuned by $B$, gate or disorder near the superconductor-insulator transition, $\rho(T)$ saturates below $T \sim 0.1\,T_c$ at $1e-3\ \text{to}\ 1e-1$ of the normal-state value. Determine whether the saturation survives when electron temperature and external radiation are independently controlled (filtered leads, shielding, noise thermometry), i.e. whether $\rho(T \to 0) > 0$ holds in a finite parameter range.
Revision 2: In $2\mathrm{D}$ superconducting films and arrays (amorphous InOx, MoGe, Ta, transition-metal dichalcogenide superconductors, Josephson-junction arrays) tuned by $B$, gate or disorder near the superconductor-insulator transition, $\rho(T)$ saturates below $T \sim 0.1\,T_c$ at $10^{-3}\ \text{to}\ 10^{-1}$ of the normal-state value. Determine whether the saturation survives when electron temperature and external radiation are independently controlled (filtered leads, shielding, noise thermometry), i.e. whether $\rho(T \to 0) > 0$ holds in a finite parameter range.
Settled by
Measurements with calibrated electron thermometry and progressively improved radiation filtering in several material classes, showing whether the saturation disappears or stays unchanged.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
contested
Status note
Radiation filtering removed the saturation in amorphous InOx and 2H-NbSe2 (Tamir et al., Science Advances 5, eaau3826, 2019), while other groups report saturation that persists with filtering in other films; no consensus as of 2026.
Posed since
(empty)

Decisions