Possible Fröhlich superconductivity in strong magnetic fields

Unconventional quantum fluid at high magnetic fields in the marginal charge-density-wave systemα−(BEDT−TTF)2MHg(

“…A simple model (Appendix), describing a new type of quantum fluid comprising a CDW coexisting with a two-dimensional Fermi-surface pocket, is able to account for the origins of the currents. Taken together, these findings are able to reconcile the body of experimental evidence [12,17,18,19,20,21,22,23,24] which had previously been interpreted in terms of the quantum Hall effect [27] or superconductivity [22]. densities ̺1D and ̺2D associated with the 1D and 2D Fermi-surface sections respectively would be subject to the conservation equation ̺1D + ̺2D + ̺ bg = 0, where ̺ bg is the density of charge due to the ionic cores.…”

“…Experimental studies of this high-magnetic-field phase, denoted CDW x , lead one to question whether it is a CDW at all. While conventional wisdom has it that CDWs constitute a class of narrow-gap insulators [1,2], experimental studies find behavior that is reminiscent either of the quantum Hall effect [17,18,19,20,21] or superconductivity [12,22,23,24]. These experimental findings include a sharp drop in the electrical resistivity at low temperatures, persistent currents and unusual Hallvoltage phenomena.…”

“…The present paper seeks to reconcile the body of experimental evidence [12,17,18,19,20,21,22,23,24] in exploring the predicted properties of a new type of quantum fluid, consisting of a CDW coexisting with a 2D Fermi surface. A simple model shows that the exchange of quasiparticles between these subsystems results in the sample partially screening time-and spatially-varying electromagnetic fields via two types of current flow; this result is supported by the experimental data in this work, which show that the screening currents observed in earlier magnetic measurements [12,17,23,24,30] comprise two parts. The first is weighted mostly towards the sample edges and can be considered a free current j free , furnishing a Hall-potential gradient.…”

Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor -(BEDT-TTF)2Cu(NCS)2

“…We therefore obtain another estimate of σ by using B to drive the sample normal at T = 0.7 K. Figure 2(c) shows that λ grows to 0.11 mm, indicating both that δ is around this size, and that the sample (r s ≈ 0.13 mm) is almost completely penetrated. Further support for this comes from the fact that no SdH oscillations are observed in λ (compare figure 2(c) with 1), whereas their observation is possible with the megahertz coil system in larger samples [27] or by increasing f . Again using δ = (πσ f µ) −1/2 , we obtain σ = 6.8 × 10 5 −1 m −1 , somewhat smaller than the value deduced at B = 0 and 12 K, and similar to, but slightly higher than, the values obtained by other methods [24,25].…”

Magnetic field dependent and induced ground states in organic conductors

“…One was the appearance of very anomalous quantum oscillations above B k which had an odd temperature dependence, and moreover, a strange diamagnetic hysteresis effect in the magnetization [119], which led to the further description of the CDW x phase above B k . This has led to speculations for some kind of Frölich-type transport mechanism of an anomalous CDW ground state in this region of the phase diagram [120].…”