论文标题
稻米模型中的非型手性对称性和孤子
Nonsymmorphic chiral symmetry and solitons in the Rice-Mele model
论文作者
论文摘要
Rice-Mele模型具有两个拓扑和空间对称阶段,即Su-Schrieffer-Heeger(SSH)相,仅具有交替跳跃,而电荷密度波(CDW)相仅具有交替的能量。 SSH阶段的手性对称性在位置空间中很强,因此在有限系统的末端和交替跳跃中的纹理的存在下将其保存下来。然而,CDW波相的手性对称性是非词的,导致交替能量中的末端或质地破坏了散装拓扑。我们考虑在有限边界条件的有限系统中存在孤子(位置空间中的纹理)。我们确定了CDW阶段中原子上的孤子的参数范围,支持局部状态,该状态位于频带间隙内,并且我们计算了该状态的非甲状化手性操作员的期望值$ p_y $,以及Soliton Electric Charge。随着孤子的空间范围的增加超出原子极限,能量水平的速度迅速或成反比宽度与宽度成正比接近零,具体取决于孤子纹理的显微镜细节。在这两种情况下,从一个$ $ p_y $的差异均与孤子宽度成反比,而费用则独立于宽度。我们研究了在存在障碍和样品对样本参数变化的情况下孤子水平的鲁棒性,与SSH相中的单个孤子水平与奇数位点进行比较。
The Rice-Mele model has two topological and spatially-inversion symmetric phases, namely the Su-Schrieffer-Heeger (SSH) phase with alternating hopping only, and the charge-density-wave (CDW) phase with alternating energies only. The chiral symmetry of the SSH phase is robust in position space, so that it is preserved in the presence of the ends of a finite system and of textures in the alternating hopping. However, the chiral symmetry of the CDW wave phase is nonsymmorphic, resulting in a breaking of the bulk topology by an end or a texture in the alternating energies. We consider the presence of solitons (textures in position space separating two degenerate ground states) in finite systems with open boundary conditions. We identify the parameter range under which an atomically-sharp soliton in the CDW phase supports a localized state which lies within the band gap, and we calculate the expectation value $p_y$ of the nonsymmorphic chiral operator for this state, and the soliton electric charge. As the spatial extent of the soliton increases beyond the atomic limit, the energy level approaches zero exponentially quickly or inversely proportionally to the width, depending on microscopic details of the soliton texture. In both cases, the difference of $p_y$ from one is inversely proportional to the soliton width, while the charge is independent of the width. We investigate the robustness of the soliton level in the presence of disorder and sample-to-sample parameter variations, comparing with a single soliton level in the SSH phase with an odd number of sites.