Disordered hyperuniformity in superconducting vortex lattices

Abstract

The current carrying capability of type II superconductors under magnetic fields is determined to a large extent by the interaction of superconducting vortices with pinning centers. Vortices are arranged in lattices with varying degrees of disorder depending on the balance between the intervortex interactions and the pinning strength. We analyze here vortex arrangements in disordered vortex lattices of different superconducting systems, single crystals (Co-doped NbSe 2 , LiFeAs, and CaKFe 4 As 4), and amorphous W-based thin films (with critical temperatures T c from 4 K to 35 K and critical fields from 3.4 T to more than 90 T). We calculate for each case the structure factor and number variance and compare to calculations on an interacting set of partially pinned particles. We find that random density fluctuations appear when pinning overcomes interactions and show that the suppression of density fluctuations is correlated to the presence of interactions. We discuss the results within the framework of hyperuniform distributions and find that all studied lattices follow a similar increase of the number variance with the defect density.

Regularity and resilience of short-range order in uniformly randomized lattices

“…where the subscript n = I, II and  S is defined in equation (7). Therefore, the structure factor of the perturbed lattice consists of two contributions: a background field characterising density fluctuations [first two terms in equation (8)] and the Bragg peaks of the underlying lattices [the third term in equation (8)]. The Bragg peaks are modulated by a multiplicative factor that reduces their amplitude at large-q more than at small-q i.e., | ( )|  F q n 2 as given in equation (5) decays to zero at large-q.…”

“…Perturbed lattices play a crucial role in the search of novel quasi-disordered materials exhibiting desirable properties such as large isotropic photonic band gaps [1,2], enhanced sunlight absorption [3][4][5][6], and high temperature superconductivity [7,8]. Randomly perturbed lattices (RPLs) are also used as toy-models for studying structure formation in a wide range of physical systems found in astronomy [9][10][11][12], biology [13,14], wireless communication [15,16], and material science [17,18].…”

Simplified feedback control system for scanning tunneling microscopy

“…The images show the superconducting vortex lattice of β −Bi 2 Pd at 0.1 T and 100 mK [38][39][40] . We can visualize results at different bias voltages, identify vortices or triangulate vortex lattices [41][42][43] . We can also use the same modules to visualize oscillations in the tunneling conductance due to impurity scattering, called quasiparticle interference.…”

Anisotropic suppression of hyperuniformity of elastic systems in media with planar disorder

“…1,2 This hidden order is the structural property of hyperuniformity, characterized by an anomalous suppression of large-scale density fluctuations in the system. This property is naturally expected in a crystal, but it is also observed in a wide variety of disordered systems such as two-dimensional material structures, [3][4][5][6][7][8] jammed particles, 9,10 bubbles in foam, 11 vortex matter in type-II superconductors, 12,13 patterns of photoreceptors in avian retinas, 14 biological tissues, 15 and even the distribution of the density fluctuations in the early Universe. 16 Hyperuniform systems present a vanishing structure factor in the infinite-wavelength or small wavenumber q limit, namely S(q) → 0 as q → 0.…”

“…12 Later, disordered hyperuniform vortex structures have been observed at high fields in several superconductors presenting weak and strong point disorder. 13 Hyperuniform vortex structures are theoretically expected for media with weak point disorder since in this case the effective interaction between vortex tips at the sample surface is long ranged. Theoretically, a suppression of hyperuniformity is expected for media with columnar correlated disorder.…”