Inside the metals, semiconductors, and magnets of our everyday
experience, electrons are uniformly distributed throughout the
material. By contrast, electrons often form clumpy patterns inside of
strongly correlated electronic systems (SCES) such as colossal
magnetoresistance materials and high temperature superconductors. In
copper-oxide based high temperature superconductors, scanning
tunneling microscopy (STM) has detected an electron nematic on the
surface of the material, in which the electrons form nanoscale
structures which break the rotational symmetry of the host crystal.
These structures may hold the key to unlocking the mystery of high
temperature superconductivity in these materials, but only if the
nematic also exists throughout the entire bulk of the material.
Using new methods we have developed for decoding these surface
structures, we find that the nematic indeed persists throughout the
bulk of the material. We furthermore find that the intricate pattern
formation is set by a delicate balance between disorder,
interactions, and material anisotropy, leading to a fractal nature of
the cluster pattern. The methods we have developed can be extended to
many other surface probes and materials, enabling surface probes to
determine whether surface structures are confined only to the surface,
or whether they extend throughout the material.
Key References: Liu, EC, et al, Phys Rev Lett., 116, 036401 (2016);
Phillabaum, EC, et al Nature Commun. 3, 915 (2012); EC, Dahmen Nature
Commun. 2, 379 (2011).