Can any material superconduct at room temperature and ambient pressure
In plain words
The best superconductor at normal pressure works up to about 151 K, roughly minus 120 degrees Celsius; whether any material can reach room temperature without huge pressure is unknown.
Precise statement
Determine whether any thermodynamically stable or long-lived metastable material has $T_c \ge 300\ \mathrm{K}$ at ambient pressure. The ambient-pressure record is 151 K in pressure-quenched HgBa2Ca2Cu3O8+d (2026). An answer is a reproduced zero-resistance and Meissner measurement above 300 K at 1 bar, or a proof that a defined class of realistic materials cannot exceed a stated $T_c$ below 300 K.
What would settle it
Independent replication of resistive and magnetic transitions above 300 K at ambient pressure.
Status in the literature
Unverified note
Pressure quench of $\mathrm{HgBa2Ca2Cu3O8}+d$ raised the ambient-pressure record from $133\,\mathrm{K}$ to $151\,\mathrm{K}$ (2026); claims of room-temperature superconductivity in nitrogen-doped lutetium hydride (2023) and LK-99 (2023) were not reproduced.