### Abstract

Much of our understanding of vibrational excitations and elasticity is based upon analysis of frames consisting of sites connected by bonds occupied by central-force springs, the stability of which depends on the average number of neighbors per site z. When z < z_{c} ≈ 2d, where d is the spatial dimension, frames are unstable with respect to internal deformations. This pedagogical review focuses on the properties of frames with z at or near z_{c}, which model systems like randomly packed spheres near jamming and network glasses. Using an index theorem, N_{0} -N_{S} = dN -N_{B} relating the number of sites, N, and number of bonds, N_{B}, to the number, N_{0}, of modes of zero energy and the number, N_{S}, of states of self stress, in which springs can be under positive or negative tension while forces on sites remain zero, it explores the properties of periodic square, kagome, and related lattices for which z = z_{c} and the relation between states of self stress and zero modes in periodic lattices to the surface zero modes of finite free lattices (with free boundary conditions). It shows how modifications to the periodic kagome lattice can eliminate all but trivial translational zero modes and create topologically distinct classes, analogous to those of topological insulators, with protected zero modes at free boundaries and at interfaces between different topological classes.

Original language | English |
---|---|

Article number | 073901 |

Pages (from-to) | 1 - 30 |

Number of pages | 30 |

Journal | Reports on Progress in Physics |

Volume | 78 |

Issue number | 7 |

Early online date | 26 Jun 2015 |

DOIs | |

Publication status | Published - 1 Jul 2015 |

### Fingerprint

### Keywords

- floppy modes
- isostaticity
- jamming
- surface phonons
- topological phonons
- vibrations of frames

### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*Reports on Progress in Physics*,

*78*(7), 1 - 30. [073901]. https://doi.org/10.1088/0034-4885/78/7/073901

**Phonons and elasticity in critically coordinated lattices.** / Lubensky, T. C.; Kane, C. L.; Mao, Xiaoming; Souslov, A.; Sun, Kai.

Research output: Contribution to journal › Article

*Reports on Progress in Physics*, vol. 78, no. 7, 073901, pp. 1 - 30. https://doi.org/10.1088/0034-4885/78/7/073901

}

TY - JOUR

T1 - Phonons and elasticity in critically coordinated lattices

AU - Lubensky, T. C.

AU - Kane, C. L.

AU - Mao, Xiaoming

AU - Souslov, A.

AU - Sun, Kai

PY - 2015/7/1

Y1 - 2015/7/1

N2 - Much of our understanding of vibrational excitations and elasticity is based upon analysis of frames consisting of sites connected by bonds occupied by central-force springs, the stability of which depends on the average number of neighbors per site z. When z < zc ≈ 2d, where d is the spatial dimension, frames are unstable with respect to internal deformations. This pedagogical review focuses on the properties of frames with z at or near zc, which model systems like randomly packed spheres near jamming and network glasses. Using an index theorem, N0 -NS = dN -NB relating the number of sites, N, and number of bonds, NB, to the number, N0, of modes of zero energy and the number, NS, of states of self stress, in which springs can be under positive or negative tension while forces on sites remain zero, it explores the properties of periodic square, kagome, and related lattices for which z = zc and the relation between states of self stress and zero modes in periodic lattices to the surface zero modes of finite free lattices (with free boundary conditions). It shows how modifications to the periodic kagome lattice can eliminate all but trivial translational zero modes and create topologically distinct classes, analogous to those of topological insulators, with protected zero modes at free boundaries and at interfaces between different topological classes.

AB - Much of our understanding of vibrational excitations and elasticity is based upon analysis of frames consisting of sites connected by bonds occupied by central-force springs, the stability of which depends on the average number of neighbors per site z. When z < zc ≈ 2d, where d is the spatial dimension, frames are unstable with respect to internal deformations. This pedagogical review focuses on the properties of frames with z at or near zc, which model systems like randomly packed spheres near jamming and network glasses. Using an index theorem, N0 -NS = dN -NB relating the number of sites, N, and number of bonds, NB, to the number, N0, of modes of zero energy and the number, NS, of states of self stress, in which springs can be under positive or negative tension while forces on sites remain zero, it explores the properties of periodic square, kagome, and related lattices for which z = zc and the relation between states of self stress and zero modes in periodic lattices to the surface zero modes of finite free lattices (with free boundary conditions). It shows how modifications to the periodic kagome lattice can eliminate all but trivial translational zero modes and create topologically distinct classes, analogous to those of topological insulators, with protected zero modes at free boundaries and at interfaces between different topological classes.

KW - floppy modes

KW - isostaticity

KW - jamming

KW - surface phonons

KW - topological phonons

KW - vibrations of frames

UR - http://www.scopus.com/inward/record.url?scp=84938149450&partnerID=8YFLogxK

U2 - 10.1088/0034-4885/78/7/073901

DO - 10.1088/0034-4885/78/7/073901

M3 - Article

VL - 78

SP - 1

EP - 30

JO - Reports on Progress in Physics

JF - Reports on Progress in Physics

SN - 0034-4885

IS - 7

M1 - 073901

ER -