Deconfined Fermi liquid to Fermi liquid transition and superconducting instability,Physical Review B

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Deconfined Fermi liquid to Fermi liquid transition and superconducting instability
Physical Review B ( IF 3.2 ) Pub Date : 2024-09-10 , DOI: 10.1103/physrevb.110.125122
Xiaofan Wu ₁ , Hui Yang ₁ , Ya-Hui Zhang ₁

Affiliation

Deconfined quantum critical points have attracted lots of attention in the past decades but were mainly restricted to incompressible phases. On the other hand, various experimental puzzles call for a new theory of unconventional quantum criticality between metals at a generic density. Here we explore the possibility of a deconfined transition between two symmetric Fermi liquids (FLs) in a bilayer model tuned by interlayer antiferromagnetic spin-spin coupling

J_{⊥}

. Across the transition the Fermi-surface volume per flavor jumps by

1 / 2

of the Brillouin zone, similar to the small to large Fermi-surface transitions in heavy fermion systems and maybe also in the high

T_{c}

cuprates. But in the bilayer case the small Fermi-surface phase (dubbed sFL) has neither symmetry breaking nor fractionalization, akin to the symmetric mass generation discussed in high-energy physics. We formulate a deconfined critical theory where the two Fermi liquids correspond to Higgs and/or confined phases of a

U (1) \times U (1)

gauge theory. We show that this deconfined FL to FL transition fixed point is unstable to pairing and thus a superconductor dome is expected at low temperature. At finite temperature above the pairing scale, microscopic electron is a composite of three deconfined fractional fermions in the critical theory. We also introduce another parameter which can suppress the pairing instability, leading to a deconfined phase stable to zero temperature. Our work opens a direction to exploring deconfined metallic criticality and pairing mechanism from critical gauge field. The transition may be relevant to the recently found nickelate superconductor

{La}_{3} {Ni}_{2} O_{7}

and future experiments in bilayer optical lattice.

中文翻译：

解禁域费米液体到费米液体的转变和超导不稳定性

过去几十年来，解禁量子临界点引起了很多关注，但主要局限于不可压缩相。另一方面，各种实验难题需要一种关于通用密度下金属之间非常规量子临界性的新理论。在这里，我们探讨了通过层间反铁磁自旋-自旋耦合调整的双层模型中两种对称费米液体（FL）之间解除限制转变的可能性

J_{⊥}

。在整个转变过程中，每种风味的费米表面体积都会跳跃

1 / 2

布里渊区，类似于重费米子系统中从小到大的费米表面跃迁，也可能在高费米子系统中

T_{c}

铜矿。但在双层情况下，小费米面相（称为 sFL）既没有对称性破缺，也没有分裂，类似于高能物理学中讨论的对称质量生成。我们制定了一个去限制临界理论，其中两种费米液体对应于希格斯和/或限制相

U (1) \times U (1)

规范理论。我们表明，这种解除限制的 FL 到 FL 转变固定点对于配对来说是不稳定的，因此预计在低温下会出现超导圆顶。在高于配对尺度的有限温度下，微观电子是临界理论中三个解禁分数费米子的复合体。我们还引入了另一个参数，它可以抑制配对不稳定性，从而导致解限相稳定在零温度。我们的工作为从临界规范场探索去限制的金属临界性和配对机制开辟了方向。这种转变可能与最近发现的镍酸盐超导体有关

{La}_{3} {Ni}_{2} O_{7}

以及双层光学晶格的未来实验。

更新日期：2024-09-11

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