Strain solitons have been observed statically in several 2D materials and dynamically in substrate materials using ultrafast laser pulses. The latter case relies on lattice relaxation in response to ultrafast heating in a light-absorbing transducer material, a process which is sensitive to the thermal expansion coefficient. Here we consider an unusual case where the sign of the thermal expansion coefficient is negative, a scenario which is experimentally feasible in light of rapid and recent advances in the discovery of negative thermal expansion materials. We present numerical solutions to a nonlinear differential equation which has been repeatedly demonstrated to quantitatively model experimental data and discuss the salient results using realistic parameters for material linear and nonlinear elasticity. The solitons that emerge from the initial value problem with negative and positive thermal expansion are qualitatively different in several ways. The new case of negative thermal expansion gives rise to a nearly-periodic soliton train with chirped profile and free of an isolated shock front. We suggest this unanticipated result may be realized experimentally and assess the potential for certain applications of this generic effect.

使用超快激光脉冲在几种二维材料中静态观察到应变孤子，在衬底材料中动态观察到应变孤子。后一种情况依赖于响应于吸光换能器材料中的超快加热的晶格弛豫，该过程对热膨胀系数敏感。在这里，我们考虑一种不寻常的情况，其中热膨胀系数的符号为负，鉴于发现负热膨胀材料的快速和最新进展，这种情况在实验上是可行的。我们提出了非线性微分方程的数值解，该方程已反复证明可对实验数据进行定量建模，并使用材料线性和非线性弹性的实际参数讨论显着结果。从具有负热膨胀和正热膨胀的初始值问题中出现的孤子在几个方面有本质的不同。负热膨胀的新情况产生了具有啁啾轮廓且没有孤立激波前沿的近周期孤子列。我们建议这种意料之外的结果可以通过实验实现，并评估这种通用效应的某些应用的潜力。