2017/10/31 by Amrit De
Physics and Astronomy · #Artificial intelligence #Cluster (spacecraft) #Computer science #Condensed matter physics #Ising model #Noise (video) #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Spins #Theoretical and Computational Physics #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevb.99.024305
published as Phys. Rev. B 99, 024305 (2019)
arxiv created 2018/12/23 · openalex created_date 2019/01/01 · openalex publication_date 2019/01/09 · arxiv updated 2019/01/16 · openalex updated_date 2026/08/05
It is shown here that 1/f^\ensuremathα flux noise in conventional low-Tc SQUIDs is a result of low temperature superparamagnetic phase transitions in small clusters of strongly correlated color center defects. The spins in each cluster interact via long-range ferromagnetic interactions. Due to its small size, the cluster behaves like a random-telegraphic macrospin when transitioning to the superparamagnetic phase. This results in 1/f^\ensuremathα noise when ensemble averaged over a random distribution of clusters. This model is self-consistent and explains all related experimental results which includes \ensuremathα\ensuremath∼0.8 independent of system size. The experimental flux-inductance-noise spectrum is explained through three-point correlation calculations and time-reversal symmetry-breaking arguments. Also, unlike the flux noise, it is shown why the second-spectrum inductance noise is inherently temperature dependent due to the fluctuation-dissipation theorem. A correlation-function calculation methodology using Ising-Glauber dynamics was key for obtaining these results.