Weak ergodicity breaking in fermionic lattice models

by Dr Kiryll Pakrouski (ETH Zürich)

Tuesday 15 Nov 2022, 11:00 → 12:00 Europe/Zurich

WHGA/121

Many-body scars are states that do not obey the eigenstate thermalization hypothesis andthus lead to weak ergodicity breaking. Time evolution starting from a mix of such statesexhibits ”revivals” - the system returns to the exact initial state after equal periods of time.We show that three families of highly symmetric states are many-body scars for any spin-1/2 fermionic Hamiltonian of the formH0+T, where T is a generator of an appropriateLie group. One of these families consists of the well-known eta-pairing states discussed byYang in the context of superconductivity. All of these states have potential advantagesfor storing and processing quantum information. We show that it is natural to chooseTto be hopping on a lattice. With this choice a number of well-known coupling terms,such as the Hubbard and the Heisenberg interactions, and the Hamiltonians containingthem (including topological ones), decompose in the required form and support the threefamilies of states as scars without fine-tuning. We also discuss the conditions for thelow-energy subspace of these models to be comprised solely of scars. We expand theframework to the non-Hermitian open systems and demonstrate that for them the scarsubspace continues to undergo coherent time evolution and exhibit ”revivals”. Finally, wediscuss the generalization of this approach to multi-band models relevant for describingexotic properties of correlated materials.Based on arXiv:2106.10300 and arXiv:2007.00845.