Juričić Vladimir, Muñoz Enrique, Soto-Garrido Rodrigo
Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110, Valparaíso 2340000, Chile.
Nordita, KTH Royal Institute of Technology and Stockholm University, Hannes Alfvéns väg 12, 106 91 Stockholm, Sweden.
Nanomaterials (Basel). 2022 Oct 24;12(21):3727. doi: 10.3390/nano12213727.
Study of the strongly correlated states in van der Waals heterostructures is one of the central topics in modern condensed matter physics. Among these, the rhombohedral trilayer graphene (RTG) occupies a prominent place since it hosts a variety of interaction-driven phases, with the metallic ones yielding exotic superconducting orders upon doping. Motivated by these experimental findings, we show within the framework of the low-energy Dirac theory that the optical conductivity can distinguish different candidates for a paramagnetic metallic ground state in this system. In particular, this observable shows a single peak in the fully gapped valence-bond state. On the other hand, the bond-current state features two pronounced peaks in the optical conductivity as the probing frequency increases. Finally, the rotational symmetry breaking charge-density wave exhibits a minimal conductivity with the value independent of the amplitude of the order parameter, which corresponds precisely to the splitting of the two cubic nodal points at the two valleys into two triplets of the band touching points featuring linearly dispersing quasiparticles. These features represent the smoking gun signatures of different candidate order parameters for the paramagnetic metallic ground state, which should motivate further experimental studies of the RTG.
对范德华异质结构中强关联态的研究是现代凝聚态物理的核心课题之一。其中，菱方三层石墨烯（RTG）占据显著地位，因为它呈现出多种相互作用驱动的相态，金属相在掺杂时会产生奇异的超导序。受这些实验发现的启发，我们在低能狄拉克理论框架内表明，光导率可以区分该系统中顺磁金属基态的不同候选态。特别是，这种可观测量在完全带隙的价键态中显示出一个单峰。另一方面，随着探测频率增加，键流态在光导率中呈现出两个明显的峰。最后，旋转对称性破缺的电荷密度波表现出最小电导率，其值与序参量的幅度无关，这恰好对应于两个谷处的两个立方节点点分裂为两个具有线性色散准粒子的能带接触点三重态。这些特征代表了顺磁金属基态不同候选序参量的确凿特征，这应该会推动对RTG的进一步实验研究。
