Abstract

Recent vigorous investigations of topological order have not only discovered new topological states of matter, but also shed new light on “already known” topological states. One established example with topological order is the valence bond solid (VBS) states in quantum antiferromagnets. The VBS states are disordered spin liquids with no spontaneous symmetry breaking, but most typically manifest a topological order known as a hidden string order on the 1D chain. Interestingly, the VBS models are based on mathematics analogous to fuzzy geometry. We review applications of the mathematics of fuzzy supergeometry in the construction of supersymmetric versions of VBS (SVBS) states and give a pedagogical introduction of SVBS models and their properties. As concrete examples, we present detailed analysis of supersymmetric versions of SU(2) and SO(5) VBS states, i.e., UOSp(N|2) and UOSp(N|4) SVBS states, whose mathematics are closely related to fuzzy two- and four-superspheres. The SVBS states are physically interpreted as hole-doped VBS states with a superconducting property that interpolates various VBS states, depending on the value of a hole-doping parameter. The parent Hamiltonians for SVBS states are explicitly constructed, and their gapped excitations are derived within the single-mode approximation on 1D SVBS chains. Prominent features of the SVBS chains are discussed in detail, such as a generalized string order parameter and entanglement spectra. It is realized that the entanglement spectra are at least doubly degenerate, regardless of the parity of bulk (super)spins. The stability of the topological phase with supersymmetry is discussed, with emphasis on its relation to particular edge (super)spin states.

Highlights

  • Correlated systems, such as cuprate superconductors, quantum Hall systems, and quantum anti-ferromagnets (QAFM), have been offering arenas for unexpected emergent phenomena brought about by strong many-body correlation

  • We reviewed the constructions and basic properties of the fuzzy superspheres and supersymmetric valence bond solid (SVBS) models

  • valence bond solid (VBS) states were emphasized based on the Schwinger operator formalism

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Summary

Introduction

Correlated systems, such as cuprate superconductors, quantum Hall systems, and quantum anti-ferromagnets (QAFM), have been offering arenas for unexpected emergent phenomena brought about by strong many-body correlation. We have already seen that the Bloch spin-coherent state enables us to relate the Laughlin-Haldane wave functions to the VBS states In correspondence with such QHE, a variety of VBS models have been constructed with the symmetries, such as SO(5), SO(2n + 1) [112,113,114], SU (N + 1) [115,116,117,118], Sp(N ) [119,120] and q-deformed SU (2) [22,23,121,122,123] [see Figure 2]. Since the MPS formalism naturally incorporates edge states, MPS provides a powerful formalism to discuss relations between topological order and edge state Taking this advantage, we can obtain general lessons for SUSY effects in topological phases. Fuzzy four-superspheres with an arbitrary number of SUSY are described in Appendix B

Fuzzy Geometry and Valence Bond Solid States
Fuzzy Two-Spheres and the Lowest Landau Level Physics
Valence Bond Solid States
Fuzzy Two-Supersphere
Construction of SVBS States
Superconducting Properties
Parent Hamiltonians
Supersymmetric Matrix Product State Formalism
Bosonic Matrix Product State Formalism
Excitations
Fixing Parent Hamiltonian
Crackion Excitation
Spin Excitation
Spinon-Hole Excitations
Topological Order
Hidden Antiferromagnetic Order and String Order Parameter
Generalized Hidden String Order in SVBS Chain
Entanglement Spectrum and Edge States
Schmidt Decomposition and Canonical Form of MPS
Supersymmetry-Protected Topological Order
Symmetry Operation and MPS
Case of SMPS
Inversion Symmetry
Time-Reversal Symmetry
String Order Parameters and Entanglement Spectrum
Higher Symmetric Generalizations
Fuzzy Four-Supersphere
Summary and Discussions
Fuzzy Four-Supersphere with Higher Supersymmetries

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