More Like this

1. Pairing symmetry and fermion projective symmetry groups

   https://doi.org/10.21468/SciPostPhys.17.6.161  

   Yang, Xu; Biswas, Sayak; Lu, Shuangyuan; Randeria, Mohit; Lu, Yuan-Ming (January 2024, SciPost Physics)

   The Ginzburg-Landau (GL) theory is very successful in describing the pairing symmetry, a fundamental characterization of the broken symmetries in a paired superfluid or superconductor. However, GL theory does not describe fermionic excitations such as Bogoliubov quasiparticles or Andreev bound states that are directly related to topological properties of the superconductor. In this work, we show that the symmetries of the fermionic excitations are captured by a Projective Symmetry Group (PSG), which is a group extension of the bosonic symmetry group in the superconducting state. We further establish a correspondence between the pairing symmetry and the fermion PSG. When the normal and superconducting states share the same spin rotational symmetry, there is a simpler correspondence between the pairing symmetry and the fermion PSG, which we enumerate for all 32 crystalline point groups. We also discuss the general framework for computing PSGs when the spin rotational symmetry is spontaneously broken in the superconducting state. This PSG formalism leads to experimental consequences, and as an example, we show how a given pairing symmetry dictates the classification of topological superconductivity. 

   more » « less
2. Algebraic higher symmetry and categorical symmetry: A holographic and entanglement view of symmetry

   https://doi.org/10.1103/PhysRevResearch.2.043086  

   Kong, Liang; Lan, Tian; Wen, Xiao-Gang; Zhang, Zhi-Hao; Zheng, Hao (October 2020, Physical Review Research)
3. Anomaly inflow, accidental symmetry, and spontaneous symmetry breaking

   https://doi.org/10.1007/JHEP01(2020)117  

   Bah, Ibrahima; Bonetti, Federico (January 2020, Journal of High Energy Physics)
4. Love symmetry

   https://doi.org/10.1007/JHEP10(2022)175  

   Charalambous, Panagiotis; Dubovsky, Sergei; Ivanov, Mikhail M. (October 2022, Journal of High Energy Physics)

   A bstract Perturbations of massless fields in the Kerr-Newman black hole background enjoy a (“Love”) SL(2 , ℝ) symmetry in the suitably defined near zone approximation. We present a detailed study of this symmetry and show how the intricate behavior of black hole responses in four and higher dimensions can be understood from the SL(2 , ℝ) representation theory. In particular, static perturbations of four-dimensional black holes belong to highest weight SL(2 , ℝ) representations. It is this highest weight properety that forces the static Love numbers to vanish. We find that the Love symmetry is tightly connected to the enhanced isometries of extremal black holes. This relation is simplest for extremal charged spherically symmetric (Reissner-Nordström) solutions, where the Love symmetry exactly reduces to the isometry of the near horizon AdS 2 throat. For rotating (Kerr-Newman) black holes one is lead to consider an infinite-dimensional SL(2 , ℝ) ⋉ $$ \hat{\textrm{U}}{(1)}_{\mathcal{V}} $$ U ̂ 1 V extension of the Love symmetry. It contains three physically distinct subalgebras: the Love algebra, the Starobinsky near zone algebra, and the near horizon algebra that becomes the Bardeen-Horowitz isometry in the extremal limit. We also discuss other aspects of the Love symmetry, such as the geometric meaning of its generators for spin weighted fields, connection to the no-hair theorems, non-renormalization of Love numbers, its relation to (non-extremal) Kerr/CFT correspondence and prospects of its existence in modified theories of gravity. 

   more » « less
5. Pumping with symmetry

   https://doi.org/10.1209/0295-5075/ad3053  

   Iglesias_Martínez, J A; Kadic, M; Laude, V; Prodan, E (April 2024, Europhysics Letters)

   Abstract Re-configurable materials and meta-materials can jump between space symmetry classes during their deformations. Here, we introduce the concept of singular symmetry enhancement, which refers to an abrupt jump to a higher symmetry class accompanied by an un-avoidable reduction in the number of dispersion bands of the excitations of the material. Such phenomenon prompts closings of some of the spectral resonant gaps along singular manifolds in a parameter space. In this work, we demonstrate that these singular manifolds can carry topological charges. As a concrete example, we show that a deformation of an acoustic crystal that encircles aconfiguration of an array of cavity resonators results in an adiabatic cycle that carries a Chern number in the bulk and displays Thouless pumping at the edges. This points to a very general guiding principle for recognizing cyclic adiabatic processes with high potential for topological pumping in complex materials and meta-materials, which rests entirely on symmetry arguments. 

   more » « less