  Local gauge symmetry is intriguing for the study of quantum thermalization
breaking. For example, in the high-spin lattice Schwinger model (LSM), the
local U(1) gauge symmetry underlies the disorder-free many-body localization
(MBL) dynamics of matter fields. This mechanism, however, would not work in a
spin-1/2 LSM due to the absence of electric energy in the Hamiltonian. In this
paper, we show that the spin-1/2 LSM can also exhibit disorder-free MBL
dynamics, as well as entropy prethermalization, by introducing a four-fermion
interaction into the system. The interplay between the fermion interaction and
U(1) gauge symmetry endows the gauge fields with an effectively disordered
potential which is responsible for the thermalization breaking. It induces
anomalous (i.e., non-thermal) behaviors in the long-time evolution of such
quantities as local observables, entanglement entropy, and correlation
functions. Our work offers a new platform to explore emergent non-thermal
dynamics in state-of-the-art quantum simulators with gauge symmetries.
