近日，奥地利因斯布鲁克大学的E. Poli与新西兰多德-沃尔斯光子与量子技术中心的D. Baillie等人合作，对二维超固体的激发进行了研究。相关研究成果已于2024年11月4日在国际知名学术期刊《物理评论A》上发表。

该研究团队对具有偶极-偶极相互作用或软核相互作用的，玻色-爱因斯坦凝聚体的二维超固态激发态进行理论研究。这种超固态由于自发破缺的连续对称性而产生三个无间隙激发分支。其中两个分支与一维超固体中的类似，与纵向声波有关。第三个分支是由二维晶体非零剪切模量产生的横波。

研究人员展示了表征密度波动的激发态和动态结构因子的数值计算结果，并研究了它们在不连续的超流体到超固体转变过程中的行为。研究表明，声波速度可以通过包含广义弹性参数（包括剪切模量）的流体动力学理论来描述。

此外，研究人员还发现，偶极超固体和软核超固体表现出不同的特性，分别属于体积不可压缩和刚性晶格极限。

附：英文原文

Title: Excitations of a two-dimensional supersolid

Author: E. Poli, D. Baillie, F. Ferlaino, P. B. Blakie

Issue&Volume: 2024/11/04

Abstract: We present a theoretical study of the excitations of the two-dimensional supersolid state of a Bose-Einstein condensate with either dipole-dipole interactions or soft-core interactions. This supersolid state has three gapless excitation branches arising from the spontaneously broken continuous symmetries. Two of these branches are related to longitudinal sound waves, similar to those in one-dimensional supersolids. The third branch is a transverse wave arising from the nonzero shear modulus of the two-dimensional crystal. We present the results of numerical calculations for the excitations and dynamic structure factor characterizing the density fluctuations and study their behavior across the discontinuous superfluid to supersolid transition. We show that the speeds of sound are described by a hydrodynamic theory that incorporates generalized elastic parameters, including the shear modulus. Furthermore, we establish that dipolar and soft-core supersolids manifest distinct characteristics, falling into the bulk-incompressible and rigid-lattice limits, respectively.

DOI: 10.1103/PhysRevA.110.053301

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.053301