三角晶格上狄拉克量子自旋液体的超导与电荷有序相
Superconducting and charge-ordered phases from Dirac quantum spin liquids on the triangular lattice
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中文总结 AI 辅助
本文提出理论框架，结合数值研究，揭示三角晶格U(1)狄拉克量子自旋液体及其衍生态经chargon希格斯凝聚形成超导、电荷有序相等丰富相的机制，构建了对应低能理论与相图。
中文摘要 AI 辅助
实验观测到三角晶格量子自旋液体绝缘体在压力或掺杂下会发生向超导性的转变，且在中红外光驱动下表现出增强的太赫兹电导率。本文提出了一个通用理论框架，用于描述由含费米子自旋子的U(1)狄拉克自旋液体，以及其有能隙的Z2和手性衍生态中，超导与电荷有序相的出现机制。数值研究已为这些自旋液体态提供了充分证据：自旋液体相包含与 emergent 规范场耦合的分数化狄拉克自旋子，而超导与电荷有序相为常规相，既无分数化激发也无 emergent 规范动力学。这些相之间的转变由无自旋、电荷为e的玻色子 chargon（“doublon”和“holon”）的希格斯凝聚驱动。研究表明，狄拉克自旋子的投影对称群唯一确定了chargon的对称性与色散关系，据此可构建chargon能带极小值附近的有效低能理论。chargon希格斯场的规范不变复合量构成了表征各相的序参量，所得相图包含丰富的有序态，包括d+id超导、电荷密度波、键密度波和对密度波。
英文摘要
Triangular-lattice quantum spin-liquid insulators are observed to undergo transitions to superconductivity under pressure or doping, and exhibit enhanced terahertz conductivity when driven by mid-infrared light. We present a general theoretical framework for the emergence of superconducting and charge-ordered phases from a U(1) Dirac spin liquid with fermionic spinons, as well as from its gapped $\mathbb{Z}_2$ and chiral descendants. Numerical studies have provided substantial evidence for these spin-liquid states. The spin-liquid phase hosts fractionalized Dirac spinons coupled to an emergent gauge field, whereas the superconducting and charge-ordered phases are conventional, with neither fractionalized excitations nor emergent gauge dynamics. The transition between these phases is driven by the Higgs condensation of spinless charge-$e$ bosonic chargons (``doublons'' and ``holons''). We show that the projective symmetry group of the Dirac spinons uniquely determines the symmetry and dispersion of the chargons, allowing us to construct an effective low-energy theory near the chargon band minima. Gauge-invariant composites of the chargon Higgs fields provide the order parameters characterizing the phases. The resulting phase diagram contains a rich variety of ordered states, including $d+id$ superconductivity, charge-density waves, bond-density waves, and pair-density waves.
