While the observation of magnetic monopoles has defied all experimental attempts
in high-energy physics
and astrophysics, sound theoretical
approaches predict they should exist, and
they have indeed been observed as quasiparticle excitations
in certain condensed-matter systems.
This indicates that, even though they are not
ubiquitous contrary to electrons, it is possible to get them as excitations above
a ground state.
In this report, we show that phonons or
lattice shear strain
generate topological monopoles in some
low-dimensional
quantum antiferromagnets.
For the Heisenberg ladder, phonons are found to generate
topological monopoles with nonzero density due
to quantum spin fluctuations.
For the four-leg Heisenberg tube, longitudinal shear stress
generates topological monopoles with density proportional
to the strain deformation. The present theory
is based on mapping the spin degrees of freedom onto spinless
fermions using the generalized Jordan-Wigner
transformation in dimensions higher than one.
The effective magnetic field generated by the motion of the spinless fermions
has non-zero divergence
when phonons or shear stress are present. A possible system where the present
kind of monopoles could be observed
is BiCu$_2$PO$_6$.