Quantum Localization Phenomena in Many-Body Systems

Quantum localization in many-body systems encompasses a spectrum of phenomena in which interactions and disorder conspire to halt thermalisation and impede transport. Beginning with Anderson localisation, which describes the absence of diffusion for non-interacting particles in disordered potentials, the field has expanded to include interacting ensembles where disorder, conservation laws and global symmetries give rise to many-body localisation (MBL). In the MBL regime, systems retain memory of initial conditions, display an emergent set of quasi-local integrals of motion and violate the eigenstate thermalisation hypothesis. At the transition between thermal and localized phases, subdiffusive transport and Griffiths effects emerge from rare-region physics, leading to anomalous scaling of entanglement growth and response functions. Beyond disorder-induced MBL, mechanisms such as Hilbert-space fragmentation, Stark localisation under a uniform field gradient and constrained dynamics in fracton models reveal ergodicity breaking even in clean settings. Experimental realisations in ultracold atoms, trapped ions, superconducting qubits and nanophotonic lattices have mapped mobility edges, engineered scarred states and demonstrated tunable entanglement at effectively infinite temperature. This body of work has profound implications for quantum information preservation, design of non-ergodic phases and the stability of coherence in quantum simulators.

Research from Nature Portfolio

Recent studies have demonstrated that discrete symmetries in interacting spin chains can fundamentally alter localisation behaviour. By analysing systems invariant under mirror and spin-flip transformations, researchers found that finite spin transport persists at infinite temperature and zero magnetisation, signalling delocalisation across all energy densities. Numerical investigations of Stark many-body localisation (Stark-MBL) and a symmetrised MBL variant reveal that breaking these symmetries leads to robust transport and precludes the emergence of an insulating phase. Moreover, coupling two systems that individually exhibit localisation can induce mutual delocalisation, underscoring the delicate balance between disorder, interactions and global symmetries. These insights refine the criteria for MBL in higher dimensions and suggest new routes for manipulating non-ergodic behaviour through symmetry engineering.

Quantum Localization Phenomena in Many-Body Systems publication trend

The graph below shows the total number of articles in quantum localization phenomena in many-body systems across all publications each year (not limited to Nature Index journals).

Technical terms

Many-body localisation: A phase in interacting quantum systems where disorder prevents thermalisation and transport, preserving local memory of the initial state.

Ergodicity breaking: The failure of a system to explore all accessible microstates, leading to non-thermal steady states.

Mobility edge: The critical energy separating localized and extended states in the spectrum of a disordered system.

Entanglement entropy: A measure of quantum correlations between subsystems, often used to diagnose phases and transitions.

Pseudolocal operator: A conserved or approximately conserved quantity that remains local under time evolution for certain states or timescales.

References

1. Absence of localization in interacting spin chains with a discrete symmetry. Nature Communications (2023).
2. Unified Theory of Local Quantum Many-Body Dynamics: Eigenoperator Thermalization Theorems. Physical Review X (2023).
3. Probing multi-mobility edges in quasiperiodic mosaic lattices. Science Bulletin (2024).
4. Disorder-tunable entanglement at infinite temperature. Science Advances (2023).
5. Ergodicity Breaking Arising from Hilbert Space Fragmentation in Dipole-Conserving Hamiltonians. Physical Review X (2020).
6. Integrals of motion in the many-body localized phase. Nuclear Physics B (2015).