SU(4) Symmetry in Twisted Bilayer Graphene: An Itinerant Perspective
SU(4) Symmetry in Twisted Bilayer Graphene: An Itinerant Perspective
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扭曲双层石墨烯中的 SU(4) 对称性：流动视角
DOI：
10.1103/physrevlett.128.227601
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发表时间：
2022
影响因子：
8.6
通讯作者：
Chubukov, Andrey V.
中科院分区：
文献类型：
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作者：
Chichinadze, Dmitry V.;Classen, Laura;Wang, Yuxuan;Chubukov, Andrey V.
我们研究了扭曲双层石墨烯在电荷中性以上的小填充和货车霍韦填充下的非对称破碎相。我们认为，在这些填充的粒子-空穴序参数的朗道泛函都有近似的SU（4）对称性，但不同的四次项的符号。我们确定了基态的序参量流形，并分析了它的激发。对于小的填充，我们发现一个强大的一阶过渡到anmanifold的订单，打破自旋谷对称性，并诱导3-1分裂的费米激发。对于货车霍韦填充，我们发现一个弱的一阶过渡到anmanifold的订单，保持了双重带退化。我们讨论了粒子-空穴序对超导电性的影响，并与强耦合方法进行了比较。
We study symmetry-broken phases in twisted bilayer graphene at small filling above charge neutrality and at van Hove filling. We argue that the Landau functionals for the particle-hole order parameters at these fillings both have an approximate SU(4) symmetry, but differ in the sign of quartic terms. We determine the order parameter manifold of the ground state and analyze its excitations. For small fillings, we find a strong first-order transition to anmanifold of orders that break spin-valley symmetry and induce a 3-1 splitting of fermionic excitations. For van Hove filling, we find a weak first-order transition to anmanifold of orders that preserves the twofold band degeneracy. We discuss the effect of particle-hole orders on superconductivity and compare with strong-coupling approaches.