TY - JOUR

T1 - Isolating long-wavelength fluctuation from structural relaxation in two-dimensional glass

T2 - Cage-relative displacement

AU - Shiba, Hayato

AU - Keim, Peter

AU - Kawasaki, Takeshi

N1 - Funding Information:
H S and T K are financially supported by JSPS KAKENHI, Grants No. JP25103010 and JP16H06018, respectively. H S is also thankful for financial support from the Building Consortia for the Development of Human Resources in Science and Technology, the Ministry of Education, Culture, Sports, Science, and Technology, Japan. The numerical calculations were performed on the SGI Altix ICE XA at the Institute for Solid State Physics, University of Tokyo, Japan.
Publisher Copyright:
© 2018 IOP Publishing Ltd.

PY - 2018/2/12

Y1 - 2018/2/12

N2 - It has recently been revealed that long-wavelength fluctuation exists in two-dimensional (2D) glassy systems, having the same origin as that given by the Mermin-Wagner theorem for 2D crystalline solids. In this paper, we discuss how to characterise quantitatively the long-wavelength fluctuation in a molecular dynamics simulation of a lightly supercooled liquid. We employ the cage-relative mean-square displacement (MSD), defined on relative displacement to its cage, to quantitatively separate the long-wavelength fluctuation from the original MSD. For increasing system size the amplitude of acoustic long wavelength fluctuations not only increases but shifts to later times causing a crossover with structural relaxation of caging particles. We further analyse the dynamic correlation length using the cage-relative quantities. It grows as the structural relaxation becomes slower with decreasing temperature, uncovering an overestimation by the four-point correlation function due to the long-wavelength fluctuation. These findings motivate the usage of cage-relative MSD as a starting point for analysis of 2D glassy dynamics.

AB - It has recently been revealed that long-wavelength fluctuation exists in two-dimensional (2D) glassy systems, having the same origin as that given by the Mermin-Wagner theorem for 2D crystalline solids. In this paper, we discuss how to characterise quantitatively the long-wavelength fluctuation in a molecular dynamics simulation of a lightly supercooled liquid. We employ the cage-relative mean-square displacement (MSD), defined on relative displacement to its cage, to quantitatively separate the long-wavelength fluctuation from the original MSD. For increasing system size the amplitude of acoustic long wavelength fluctuations not only increases but shifts to later times causing a crossover with structural relaxation of caging particles. We further analyse the dynamic correlation length using the cage-relative quantities. It grows as the structural relaxation becomes slower with decreasing temperature, uncovering an overestimation by the four-point correlation function due to the long-wavelength fluctuation. These findings motivate the usage of cage-relative MSD as a starting point for analysis of 2D glassy dynamics.

KW - colloids

KW - dynamic correlation length

KW - low-dimensional system

KW - molecular dynamics simulation

KW - slow glassy relaxation

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U2 - 10.1088/1361-648X/aaa8b8

DO - 10.1088/1361-648X/aaa8b8

M3 - Article

C2 - 29345245

AN - SCOPUS:85042320460

VL - 30

JO - Journal of Physics Condensed Matter

JF - Journal of Physics Condensed Matter

SN - 0953-8984

IS - 9

M1 - 094004

ER -