Disorder-Induced Static Antiferromagnetism in Cuprate Superconductors

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Disorder-Induced Static Antiferromagnetism in
Cuprate Superconductors Peter Hirschfeld, U.
Florida B.M. Andersen et al. Phys. Rev. Lett. 99,
147002 (2007).
There is much evidence to suggest that the
cuprate high temperature superconductors are
unusual because of their proximity to a magnetic
state. In the past several years, several kinds
of experimental probes have reported seeing
long-range antiferromagnetic order in the
superconducting state at low temperatures in the
material La1-xSrxCuO4. This does not occur in
the cleaner cuprate materials like YBa2Cu3O7. We
proposed that each impurity induces a small
magnetic droplet around itself, and that
quasi-long range magnetic order occurs when these
bubbles overlap. To test this hypothesis, we
performed simulations of a d-wave superconductor
in the presence of local Coulomb interactions and
nonmagnetic disorder.
Simulation of magnetic order created by disorder
in LSCO
Schematic of several impurity induced droplets
overlapping
d)
c)
Structure factor S(q) obtained from
magnetization in (b)
Structure factor from Lake et al experiment
Conclusion dopant disorder accounts for static
(quasi) long range antiferromagnetic order in
intrinsically doped systems like La1-xSrxCuO4
Lake et al (2002) measured the effective magnetic
moment in an applied magnetic field using elastic
neutron scattering. Even in zero field, however,
they saw a surprisingly large signal!