Speaker
Description
Fracton phases are a particularly exotic type of quantum spin liquids
where the elementary quasiparticles are intrinsically immobile. These
phases may be described by unconventional gauge theories known as tensor
or multipolar gauge theories, characteristic for so-called type-I or
type-II fracton phases, respectively. Both variants have been associated
with distinctive singular patterns in the spin structure factor, such as
multifold pinch points for type-I and quadratic pinch points for type-II
fracton phases. Here, we assess the impact of quantum fluctuations on
these patterns by numerically investigating the spin S=1/2 quantum version
of a classical spin model on the octahedral lattice featuring exact
realizations of multifold and quadratic pinch points, as well as an
unusual pinch line singularity. Based on large scale pseudofermion and
pseudo-Majorana functional renormalization group calculations, we take the
intactness of these spectroscopic signatures as a measure for the
stability of the corresponding fracton phases. We find that in all three
cases, quantum fluctuations significantly modify the shape of pinch points
or lines by smearing them out and shifting signal away from the
singularities in contrast to effects of pure thermal fluctuations. This
indicates possible fragility of these phases and allows us to identify
characteristic fingerprints of their remnants. Besides discussing fracton
candidate phases, this talk also briefly introduces the pseudofermion and
pseudo-Majorana functional renormalization group methods and demonstrates
their strengths in numerically investigating frustrated quantum spin
systems.
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