Abstract
Topologically ordered phases of matter, although stable against local perturbations, are usually restricted to relatively small regions in phase diagrams. Thus, their preparation requires a precise fine-tunning of the system’s parameters, a very challenging task in most experimental setups. In this work, we investigate a model of spinless fermions interacting with dynamical gauge fields on a cross-linked ladder and show evidence of topological order throughout the full parameter space. In particular, we show how a magnetic flux is spontaneously generated through the ladder due to an Aharonov-Bohm instability, giving rise to topological order even in the absence of a plaquette term. Moreover, the latter coexists here with a symmetry-protected topological phase in the matter sector, which displays fractionalized gauge-matter edge states and intertwines with it by a flux-threading phenomenon. Finally, we unveil the robustness of these features through a gauge frustration mechanism, akin to geometric frustration in spin liquids, allowing topological order to survive to arbitrarily large quantum fluctuations. In particular, we show how, at finite chemical potential, topological solitons are created in the gauge field configuration, which bound to fermions and form deconfined quasiparticles. The simplicity of the model makes it an ideal candidate for 2D gauge theory phenomena, as well as exotic topological effects, to be investigated using cold-atom quantum simulators.
- Received 3 March 2020
- Revised 28 May 2020
- Accepted 14 August 2020
DOI:https://doi.org/10.1103/PhysRevX.10.041007
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
At low temperatures, certain quantum systems evade the standard forms of ordering that give rise to usual phases of matter, such as crystalline solids or magnetic materials. Instead, strong quantum correlations between their constituent particles lead to configurations characterized by topological order, where distinct global properties are protected against local perturbations. This allows one to encode information in a nonlocal manner, providing a promising avenue to fault-tolerant quantum computation. However, preparing such quantum states is a challenging experimental task, requiring a precise fine-tuning of the system’s parameters. In this work, we identify two mechanisms that could allow topological order to be found under more relaxed conditions in near-term atomic experiments.
In particular, we study a gauge theory model whose main building blocks have already been implemented using ultracold atoms in optical lattices. The use of gauge theories, characterized by local symmetries, is ubiquitous in theoretical physics, ranging from the description of fundamental particles such as quarks to the physics behind high-temperature superconductors.
In our model, we first show how an internal magnetic field is spontaneously generated, bringing about topological order to the system. Then, we identify a mechanism that allows these effects to survive under arbitrary, large fluctuations. This mechanism also leads to the presence of deconfined quasiparticles in the spectrum, another interesting but partially unexplored feature of gauge theories connected to open questions in particle physics.
Our results indicate the existence of novel methods to experimentally address strongly correlated topological effects, which are relevant to condensed matter and high-energy physics, using controllable atomic systems.
