Is kinetic constraint sufficient to generate quantum many-body scars ?

The discovery of "Quantum many-body scars (QMBS)" has been a milestone in
many-body
physics as it revolutionized our concept about interacting and non-integrable
quantum many-body
systems. QMBS are atypical eigenstates whose presence weakly violates Eigenstate
thermalization
hypothesis (ETH) in a system. QMBS were first discovered in kinetically constrained
Rydberg atom
arrays followed by other systems without kinetic constraint. But ironically the
mechanism of
scarring in systems with kinetic constraint has remained poorly understood to date.
In this talk,
I will first briefly review the relevant portion of the literature followed by our
contribution in
resolving the mystery. I will discuss why higher spin PXP models are ideal platforms
to explore
the role of kinetic constraint in generating QMBS. Constraint engineering can be
used to
synthesize non-integrable models with Hilbert space fragmentation, extensive number
of conserved
quantities and strong ergodicity which I will demonstrate using three different
spin-1 PXP models.

Ref: [1] Bernien, H., Schwartz, S., Keesling, A. et al. Probing many-body dynamics
on a 51-atom
quantum simulator. Nature 551, 579–584 (2017).
  [2] Turner, C.J., Michailidis, A.A., Abanin, D.A. et al. Weak ergodicity breaking
from quantum
many-body scars. Nature Phys 14, 745–749 (2018).
  [3] Bhaskar Mukherjee, Zi Cai, and W. Vincent Liu. Constraint-induced breaking and
restoration
of ergodicity in spin-1 PXP models. Phys. Rev. Research 3, 033201 (2021).