Unconventionally large quantum-dissipative gap regime in overdoped Bi₂Sr₂CaCu₂O_8+y

We report on an unexpectedly extensive dissipative gapped regime in the zero-temperature (quantum) limit in highly overdoped Bi2Sr2CaCu2O8+y. Using high-field interlayer resistivity measurements we show that as T→0 the magnetic field that closes the pseudogap and the upper critical field Hc2 coincide, uniquely defining the upper limit on the vortex state. By mapping the upper and lower bounds on the molten vortex state, we find the gapped quantum fluctuation regime stretching from ∼30 to 70 T. This exceeds by far the conventional estimates, pointing to the anomalous gapped nature of the strongly overdoped regime.