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Many-Body Delocalization via Emergent Symmetry
N S Srivatsa1, Roderich Moessner1, Anne E B Nielsen1
1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany.
Physical Review Letters
|January 7, 2021
Summary
An emergent symmetry can protect quantum states from many-body localization (MBL). This study demonstrates a Z_{2} symmetric model where a protected state avoids MBL, even with nonlocal interactions and disorder.
Area of Science:
- Quantum physics
- Condensed matter physics
- Statistical mechanics
Background:
- Many-body localization (MBL) prevents thermalization in isolated quantum systems.
- Understanding MBL is crucial for quantum information science and condensed matter theory.
- Emergent symmetries are key to novel quantum phenomena.
Purpose of the Study:
- To investigate if emergent symmetries can protect quantum states from many-body localization.
- To propose and analyze a novel quantum model exhibiting such protection.
- To explore the behavior of MBL in the presence of nonlocal, structured interactions.
Main Methods:
- Development of a Z_{2} symmetric model with nonlocal interactions.
- Analytical investigation of the ground state's SU(2) invariance.
- Numerical analysis of system states at large disorder strength.
- Perturbation analysis to study symmetry breaking effects.
Main Results:
- A Z_{2} symmetric model with nonlocal interactions was proposed.
- An emergent SU(2) symmetry was identified, protecting the ground state from MBL.
- Finite energy density states exhibited glassy MBL, while the lowest energy states remained delocalized.
- Perturbing the emergent SU(2) symmetry led to localization of the protected state.
- The model demonstrated MBL with structured, nonlocal disordered interactions.
- A method to move the protected state into the bulk spectrum was shown.
Conclusions:
- Emergent symmetries offer a robust mechanism to protect quantum states from many-body localization.
- The proposed model provides a concrete platform for studying MBL and symmetry protection.
- This work opens new avenues for controlling localization and thermalization in quantum systems.
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