2015/11/30 by M. H. Hamidian, Mohammad Hamidian, Stephen Edkins +15
Physics and Astronomy · #Charge density wave #Condensed matter physics #Cooper pair #Cuprate #Density of states #Density wave theory #Force Microscopy Techniques and Applications #Physics #Physics of Superconductivity and Magnetism #Pseudogap #Quantum mechanics #Quantum tunnelling #Superconductivity #Surface and Thin Film Phenomena #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1038/nature17411
published as Nature 532, 343 (2016)
arxiv created 2016/01/21 · openalex publication_date 2016/04/12 · arxiv updated 2016/04/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
The quantum condensate of Cooper-pairs forming a superconductor was originally conceived to be translationally invariant. In theory, however, pairs can exist with finite momentum Q and thereby generate states with spatially modulating Cooper-pair density. While never observed directly in any superconductor, such a state has been created in ultra-cold 6Li gas. It is now widely hypothesized that the cuprate pseudogap phase contains such a 'pair density wave' (PDW) state. Here we use nanometer resolution scanned Josephson tunneling microscopy (SJTM) to image Cooper-pair tunneling from a d-wave superconducting STM tip to the condensate of Bi2Sr2CaCu2O8+x. Condensate visualization capabilities are demonstrated directly using the Cooper-pair density variations surrounding Zn impurity atoms and at the Bi2Sr2CaCu2O8+x crystal-supermodulation. Then, by using Fourier analysis of SJTM images, we discover the direct signature of a Cooper-pair density modulation at wavevectors Qp ≈ (0.25,0)2π/ a0;(0,0.25)2π/ a0 in Bi2Sr2CaCu2O8+x. The amplitude of these modulations is ~5% of the homogenous condensate density and their form factor exhibits primarily s/s'-symmetry. This phenomenology is expected within Ginzburg-Landau theory when a charge density wave with d-symmetry form factor and wave vector Qc=Qp coexists with a homogeneous d-symmetry superconductor ; it is also encompassed by several contemporary microscopic theories for the pseudogap phase.