论文标题
有吸引力的哈伯德模型作为$（3）$竞争阶段系统：超莫利德订单及其热融化
The attractive Hubbard model as an $SO(3)$ system of competing phases: supersolid order and its thermal melting
论文作者
论文摘要
超导性和充电顺序之间的竞争是当代凝结物理学的反复主题。这是在有吸引力的哈伯德模型中典型捕获的，这是一个简单的理论模型，可以直接调整比赛。在当前作者的先前研究中，有人提出，哈伯德模型将$（3）$非线性Sigma模型映射为阶段竞争变得明显。在本文中，我们严格地证明了该映射，并使用它来研究超固体的热无序。从在轨道场的存在下，从有吸引力的哈伯德模型开始，我们采用了伪造描述出现的强耦合的极限。平面伪旋转组件代表超导配对，而平面组件编码电荷密度波阶。我们获得了有效的自旋$ 1/2 $ hamiltonian，其平面内耦合和抗铁磁Z-Z耦合。此外，轨道场产生与磁性单元相同的周期性的纹理dzyaloshinskii-moriya相互作用。为了检查该自旋模型中有序的性质，我们将其考虑在经典限制中。我们假设逐渐变化的字段，导致$（3）$非线性Sigma模型描述。作为这些想法的应用，我们研究了使用模拟退火和经典的蒙特卡洛模拟的订购性质。基态代表具有共存超导性和电荷顺序的超固体。它可以看作是“梅隆晶体”，这是带电荷芯的超导涡流的常规排列。核心区域的连贯重叠产生了连贯的长期电荷顺序。随着温度的升高，该电荷顺序通过Ising通用类别的急剧相变而损失。
Competition between superconductivity and charge order is a recurring theme in contemporary condensed matter physics. This is quintessentially captured in the attractive Hubbard model, a simple theoretical model where the competition can be directly tuned. In previous studies by the current authors, it has been suggested that the Hubbard model maps to an $SO(3)$ non-linear sigma model, where the phase competition becomes manifest. In this article, we rigorously demonstrate this mapping and use it to study thermal disordering of a supersolid. Starting with the attractive Hubbard model in the presence of an orbital field, we take the limit of strong coupling where a pseudospin description emerges. The in-plane pseudospin components represent superconducting pairing while the out-of-plane component encodes charge density wave order. We obtain an effective spin-$1/2$ Hamiltonian with ferromagnetic in-plane couplings and antiferromagnetic z-z couplings. In addition, the orbital field gives rise to a textured Dzyaloshinskii-Moriya interaction that has the same periodicity as the magnetic unit cell. In order to examine the nature of ordering in this spin model, we consider it in the classical limit. We assume slowly varying fields, leading to the $SO(3)$ non-linear sigma model description. As an application of these ideas, we study the nature of ordering using simulated annealing and classical Monte Carlo simulations. The ground state represents a supersolid with coexisting superconductivity and charge order. It can be viewed as a `meron crystal', a regular arrangement of superconducting vortices with charge-ordered cores. The coherent overlap of core regions gives rise to coherent long-ranged charge order. As the temperature is raised, this charge order is lost via a sharp phase transition in the Ising universality class.
