Strong Hilbert space fragmentation via emergent quantum drums in two dimensions

We introduce a disorder-free model of $S=1/2$ spins on the square lattice in a constrained Hilbert space where two up-spins are not allowed simultaneously on any two neighboring sites of the lattice. The interactions are given by ring-exchange terms on elementary plaquettes that conserve both the to...

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Main Author: Anwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab Sen
Format: Article
Language:English
Published: SciPost 2023-06-01
Series:SciPost Physics
Online Access:https://scipost.org/SciPostPhys.14.6.146
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author Anwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab Sen
author_facet Anwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab Sen
author_sort Anwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab Sen
collection DOAJ
description We introduce a disorder-free model of $S=1/2$ spins on the square lattice in a constrained Hilbert space where two up-spins are not allowed simultaneously on any two neighboring sites of the lattice. The interactions are given by ring-exchange terms on elementary plaquettes that conserve both the total magnetization as well as dipole moment. We show that this model provides a tractable example of strong Hilbert space fragmentation in two dimensions with typical initial states evading thermalization with respect to the full Hilbert space. Given any product state, the system can be decomposed into disjoint spatial regions made of edge and/or vertex sharing plaquettes that we dub as "quantum drums". These quantum drums come in many shapes and sizes and specifying the plaquettes that belong to a drum fixes its spectrum. The spectra of some small drums is calculated analytically. We study two bigger quasi-one-dimensional drums numerically, dubbed "wire" and a "junction of two wires" respectively. We find that these possess a chaotic spectrum but also support distinct families of quantum many-body scars that cause periodic revivals from different initial states. The wire is shown to be equivalent to the one-dimensional PXP chain with open boundaries, a paradigmatic model for quantum many-body scarring; while the junction of two wires represents a distinct constrained model.
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spelling doaj.art-e958357982c048ad94b26f9fcff0b8662023-06-07T13:08:00ZengSciPostSciPost Physics2542-46532023-06-0114614610.21468/SciPostPhys.14.6.146Strong Hilbert space fragmentation via emergent quantum drums in two dimensionsAnwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab SenWe introduce a disorder-free model of $S=1/2$ spins on the square lattice in a constrained Hilbert space where two up-spins are not allowed simultaneously on any two neighboring sites of the lattice. The interactions are given by ring-exchange terms on elementary plaquettes that conserve both the total magnetization as well as dipole moment. We show that this model provides a tractable example of strong Hilbert space fragmentation in two dimensions with typical initial states evading thermalization with respect to the full Hilbert space. Given any product state, the system can be decomposed into disjoint spatial regions made of edge and/or vertex sharing plaquettes that we dub as "quantum drums". These quantum drums come in many shapes and sizes and specifying the plaquettes that belong to a drum fixes its spectrum. The spectra of some small drums is calculated analytically. We study two bigger quasi-one-dimensional drums numerically, dubbed "wire" and a "junction of two wires" respectively. We find that these possess a chaotic spectrum but also support distinct families of quantum many-body scars that cause periodic revivals from different initial states. The wire is shown to be equivalent to the one-dimensional PXP chain with open boundaries, a paradigmatic model for quantum many-body scarring; while the junction of two wires represents a distinct constrained model.https://scipost.org/SciPostPhys.14.6.146
spellingShingle Anwesha Chattopadhyay, Bhaskar Mukherjee, Krishnendu Sengupta, Arnab Sen
Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
SciPost Physics
title Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
title_full Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
title_fullStr Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
title_full_unstemmed Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
title_short Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
title_sort strong hilbert space fragmentation via emergent quantum drums in two dimensions
url https://scipost.org/SciPostPhys.14.6.146
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