金属反铁磁性开始时的非受限临界和鬼费米面
Deconfined criticality and ghost Fermi surfaces at the onset of antiferromagnetism in a metal
摘要：
我们提出了一个一般的理论框架，使用两层的辅助量子比特，与一个大的费米表面的费米液体，和一个伪间隙金属与一个小的费米表面的类电子准粒子之间的临界性解除限制。赝带隙金属可以是磁有序的金属，或者没有磁有序的分级费米液体（FL*）。临界的“鬼”费米面出现在跃迁处（在大电子费米面旁边），鬼费米子既不带自旋也不带电荷，但与$(U(1) \times U(1))/Z_2$或$(SU(2) \times U(1))/Z_2$规范场的耦合最小。$(U(1) \times U(1))/Z_2$的例子描述了近藤击穿和磁序的同时发生：两个规范场在鬼费米面激发之间产生几乎相等的吸引和排斥相互作用，这种竞争控制了量子临界性。远离赝能隙侧的跃迁，鬼费米面吸收部分大电子费米面，导致霍尔系数的跳跃。我们还发现了一个例子之间的“不必要的量子临界点”的自旋密度波秩序的金属，和一个金属的本地矩磁秩序。幽灵费米子在跃迁附近贡献了增强的比热，并且也可以在其他热探针中检测到。我们将我们的结果与相关电子化合物的相位。
英文摘要：
We propose a general theoretical framework, using two layers of ancilla qubits, for deconfined criticality between a Fermi liquid with a large Fermi surface, and a pseudogap metal with a small Fermi surface of electron-like quasiparticles. The pseudogap metal can be a magnetically ordered metal, or a fractionalized Fermi liquid (FL*) without magnetic order. A critical 'ghost' Fermi surface emerges (alongside the large electron Fermi surface) at the transition, with the ghost fermions carrying neither spin nor charge, but minimally coupled to $(U(1) \times U(1))/Z_2$ or $(SU(2) \times U(1))/Z_2$ gauge fields. The $(U(1) \times U(1))/Z_2$ case describes simultaneous Kondo breakdown and onset of magnetic order: the two gauge fields induce nearly equal attractive and repulsive interactions between ghost Fermi surface excitations, and this competition controls the quantum criticality. Away from the transition on the pseudogap side, the ghost Fermi surface absorbs part of the large electron Fermi surface, and leads to a jump in the Hall co-efficient. We also find an example of an "unnecessary quantum critical point" between a metal with spin density wave order, and a metal with local moment magnetic order. The ghost fermions contribute an enhanced specific heat near the transition, and could also be detected in other thermal probes. We relate our results to the phases of correlated electron compounds.
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