Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

Abstract

Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T—the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

Superconducting fluctuations observed far above T$_\mathrm{c}$ in the isotropic superconductor K$_3$C$_{60}$

“…This yielded a value of about 39T, corresponding to a zero-temperature coherence length of ξ 0 = Φ 0 /2πµ 0 H c2 (0) = 2.9nm (here Φ 0 is the magnetic flux quantum). This lies within the range of values extrapolated from other experiments [9,10], and closely matches the value recently determined using pulsed fields in a range exceeding H c2 [30].…”

Near‐Infrared Switchable Fullerene‐Based Synergy Therapy for Alzheimer's Disease

“…Fullerenes were discovered in 1985, and have been the third major carbon allotrope after diamond and graphite. Owing to the superior electrical, thermal, chemical, and mechanical properties, fullerenes have received considerable attention in many fields like photovoltaics, energy conversion and storage, superconducting materials, catalysis, and host–guest chemistry . After functionalized with hydrophilic groups or amphiphilic molecules, water‐soluble fullerenes also infiltrate into various biological applications such as theranostics, gene/drug delivery, biosensing, antiviral, and cell scaffold …”

Pressure-induced valence transition in the mixed-valence (Sm1/3Ca2/3)2.75C60 fulleride

“…2,3 To date, metal fulleride research has been dominated by work on alkali fullerides, especially those with stoichiometry A 3 C 60 (A = alkali metal). These have emerged as archetypal strongly correlated systems with superconducting transition temperatures, T c as high as 38 K 4 and upper critical magnetic fields, H c2 in excess of 90 T. 5 Nonetheless the electronic properties are entirely dominated by the narrow band behaviour of the C 60 anion sublattice -the supporting cation sublattice is invariably electronically inactive and only plays a charge-balancing role as a structural spacer. 6 A comparable but exactly reverse situation is encountered in rare earth compounds which represent one of the most fascinating classes of strongly correlated systems that include Kondo insulators and heavy fermions.…”