TY - JOUR
T1 - Defect Unbinding in Active Nematics
AU - Shankar, Suraj
AU - Ramaswamy, Sriram
AU - Marchetti, M. Cristina
AU - Bowick, Mark J.
N1 - Funding Information:
We thank Ananyo Maitra and Mike Cates for insightful comments. This work was supported by the National Science Foundation at Syracuse University through Grants No. DMR-1609208 (M. C. M. and S. S.) and No. DGE-1068780 (M. C. M.) and at KITP under Grant No. PHY-1748958. M. C. M., M. J. B., and S. S. thank the Syracuse Soft and Living Matter Program for support. All authors thank the Simons Foundation for support and the KITP for hospitality in the course of this work. S. R. acknowledges the support of the Tata Education and Development Trust, and a J. C. Bose Fellowship of the Science & Engineering Research Board, India.
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/9/7
Y1 - 2018/9/7
N2 - We formulate the statistical dynamics of topological defects in the active nematic phase, formed in two dimensions by a collection of self-driven particles on a substrate. An important consequence of the nonequilibrium drive is the spontaneous motility of strength +1/2 disclinations. Starting from the hydrodynamic equations of active nematics, we derive an interacting particle description of defects that includes active torques. We show that activity, within perturbation theory, lowers the defect-unbinding transition temperature, determining a critical line in the temperature-activity plane that separates the quasi-long-range ordered (nematic) and disordered (isotropic) phases. Below a critical activity, defects remain bound as rotational noise decorrelates the directed dynamics of +1/2 defects, stabilizing the quasi-long-range ordered nematic state. This activity threshold vanishes at low temperature, leading to a reentrant transition. At large enough activity, active forces always exceed thermal ones and the perturbative result fails, suggesting that in this regime activity will always disorder the system. Crucially, rotational diffusion being a two-dimensional phenomenon, defect unbinding cannot be described by a simplified one-dimensional model.
AB - We formulate the statistical dynamics of topological defects in the active nematic phase, formed in two dimensions by a collection of self-driven particles on a substrate. An important consequence of the nonequilibrium drive is the spontaneous motility of strength +1/2 disclinations. Starting from the hydrodynamic equations of active nematics, we derive an interacting particle description of defects that includes active torques. We show that activity, within perturbation theory, lowers the defect-unbinding transition temperature, determining a critical line in the temperature-activity plane that separates the quasi-long-range ordered (nematic) and disordered (isotropic) phases. Below a critical activity, defects remain bound as rotational noise decorrelates the directed dynamics of +1/2 defects, stabilizing the quasi-long-range ordered nematic state. This activity threshold vanishes at low temperature, leading to a reentrant transition. At large enough activity, active forces always exceed thermal ones and the perturbative result fails, suggesting that in this regime activity will always disorder the system. Crucially, rotational diffusion being a two-dimensional phenomenon, defect unbinding cannot be described by a simplified one-dimensional model.
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U2 - 10.1103/PhysRevLett.121.108002
DO - 10.1103/PhysRevLett.121.108002
M3 - Article
AN - SCOPUS:85053107991
SN - 0031-9007
VL - 121
JO - Physical Review Letters
JF - Physical Review Letters
IS - 10
M1 - 108002
ER -