Shrinking of the Cooper Pair Insulator Phase in Thin Films with Ultrasmall Superconducting Islands (original) (raw)
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Superinsulator–superconductor duality in two dimensions
Annals of Physics, 2013
For nearly a half century the dominant orthodoxy has been that the only effect of the Cooper pairing is the state with zero resistivity at finite temperatures, superconductivity. In this work we demonstrate that by the symmetry of the Heisenberg uncertainty principle relating the amplitude and phase of the superconducting order parameter, Cooper pairing can generate the dual state with zero conductivity in the finite temperature range, superinsulation. We show that this duality realizes in the planar Josephson junction arrays (JJA) via the duality between the Berezinskii-Kosterlitz-Thouless (BKT) transition in the vortex-antivortex plasma, resulting in phase-coherent superconductivity below the transition temperature, and the charge-BKT transition occurring in the insulating state of JJA and marking formation of the low-temperature charge-BKT state, superinsulation. We find that in disordered superconducting films that are on the brink of superconductor-insulator transition the Coulomb forces between the charges acquire two-dimensional character, i.e. the corresponding interaction energy depends logarithmically upon charge separation, bringing the same vortex-charge-BKT transition duality, and realization of superinsulation in disordered films as the low-temperature charge-BKT state. Finally, we discuss possible applications and utilizations of superconductivity-superinsulation duality.
A strange metal in a bosonic system
2021
Fermi liquid theory forms the basis for our understanding of the majority of metals, which is manifested in the description of transport properties that the electrical resistivity goes as temperature squared in the limit of zero temperature. However, the observations of strange metal states in various quantum materials, notably high-temperature superconductors, bring this spectacularly successful theoretical framework into crisis. When electron scattering rate 1/τ hits its limit, kBT/ħ where ħ is the reduced Planck's constant, T represents absolute temperature and kB denotes Boltzmann's constant, Planckian dissipation occurs and lends strange metals a surprising link to black holes, gravity, and quantum information theory. Here, we show the characteristic signature of strange metallicity arising unprecedentedly in a bosonic system. Our nanopatterned YBa2Cu3O7-δ(YBCO) film arrays reveal T-linear resistance as well as B-linear magnetoresistance over an extended temperature and...
2007
We have observed multiple magnetic field driven superconductor to insulator transitions (SIT) in amorphous Bi films perforated with a nano-honeycomb (NHC) array of holes. The period of the magneto-resistance, H = HM = h/2eS where S is the area of a unit cell of holes, indicates the field driven transitions are boson dominated. The field-dependent resistance follows R(T) = R0(H)e T 0 (H)/T on both sides of the transition so that the evolution between these states is controlled by the vanishing of T0 → 0. We compare our results to the thickness driven transition in NHC films and the field driven transitions in unpatterned Bi films, other materials, and Josephson junction arrays. Our results suggest a structural source for similar behavior found in some materials and that despite the clear bosonic nature of the SITs, quasiparticle degrees of freedom likely also play an important part in the evolution of the SIT.
Physical Review B, 2008
We have observed multiple magnetic field driven superconductor-to-insulator transitions ͑SIT͒ in amorphous Bi films perforated with a nanohoneycomb ͑NHC͒ array of holes. The period of the magnetoresistance, H = H M = h / 2eS, where S is the area of a unit cell of holes, indicates that the field driven transitions are boson dominated. The field-dependent resistance follows R͑T͒ = R 0 ͑H͒e T 0 ͑H͒/T on both sides of the transition so that the evolution between these states is controlled by the vanishing of T 0 → 0. We compare our results to the thickness driven transition in NHC films and the field driven transitions in unpatterned Bi films, other materials, and Josephson junction arrays. Our results suggest a structural source for similar behavior found in some materials and that despite the clear bosonic nature of the SITs, quasiparticle degrees of freedom likely also play an important part in the evolution of the SIT.
Quantum coherence across bosonic superconductor-anomalous metal-insulator transitions
arXiv: Superconductivity, 2019
After decades of explorations, suffering from low critical temperature and subtle nature, whether a metallic ground state exists in a two-dimensional system beyond Anderson localization is still a mystery. Supremely, phase coherence could be the key that unlocks its intriguing nature. This work reveals how quantum phase coherence evolves across bosonic superconductor-metal-insulator transitions via magneto-conductance quantum oscillations in high-Tc superconducting films. A robust intervening anomalous metallic state characterized by both resistance and oscillation amplitude saturations in the low temperature regime is detected. By contrast, with decreasing temperature the oscillation amplitude monotonically grows on the superconducting side, but decreases at low temperatures on the insulating side. It suggests that the saturation of phase coherence plays a prominent role in the formation of this anomalous metallic state.
Intermediate bosonic metallic state in the superconductor-insulator transition
Science, 2019
Whether a metallic ground state exists in a two-dimensional system beyond Anderson localization remains an unresolved question. Here, we study how quantum phase coherence evolves across superconductor-metal-insulator transitions via magneto-conductance quantum oscillations in nanopatterned high-temperature superconducting films. We tune the degree of phase coherence by varying the etching time of our films. Between the superconducting and insulating regimes, we detect a robust intervening anomalous metallic state characterized by saturating resistance and oscillation amplitude at low temperatures. Our measurements suggest that the anomalous metallic state is bosonic and that the saturation of phase coherence plays a prominent role in its formation.