标题： 费米体积改变的量子相变穿越热电功率无平移对称性破缺 显示英文标题

标题： Thermopower across Fermi-volume-changing quantum phase transitions without translational symmetry breaking

摘要： 我们描述了在无平移对称性破缺的肯德里奇（Kondo）晶格模型中，穿越费米体积改变量子相变时低温热电功率的演化过程。这一转变从具有常规Luttinger体积大费米表面的重费米液体状态移动到一个“FL*”态，该状态以小费米表面和带有分数化激发的自旋液体为特征。大费米表面相的出现是由一种在新兴U(1)规范场中携带单位规范电荷的Higgs场凝聚引起的。我们考虑了空间随机Kondo交换的情况，因为这会导致电输运中的奇异金属行为。我们在一个“偏斜”的边缘费米液体中发现了大的不对称热电功率，与Georges和Mravlje的偏斜非费米液体（arXiv:2102.13224）有相似之处。我们的发现与重费米子化合物中的近期观测结果一致（Z.-Y. Cao等人，arXiv:2408.13604），并描述了大费米表面一侧热电功率的增强以及小费米表面一侧的非单调行为。我们的结果也适用于单带Hubbard模型和铜氧化物中的伪能隙转变。在辅助框架下，单带模型表现出反向的Kondo晶格转变：小费米表面伪能隙态对应于凝聚的Higgs态。这种反转导致我们的理论中伪能隙一侧热电功率的增强，与铜氧化物中的观测结果一致（C. Collignon等人，arXiv:2011.14927；A. Gourgout等人，arXiv:2106.05959）。我们认为这些观测结果支持非对称破缺的费米体积改变跃迁作为铜氧化物中伪能隙开始的潜在描述。 显示英文摘要

摘要： We describe the evolution of low-temperature thermopower across Fermi-volume-changing quantum phase transitions in Kondo lattice models without translational symmetry breaking. This transition moves from a heavy Fermi liquid with a conventional Luttinger-volume large Fermi surface to a 'FL*' state, characterized by a small Fermi surface and a spin liquid with fractionalized excitations. The onset of the large Fermi surface phase is driven by the condensation of a Higgs field that carries a unit gauge charge under an emergent U(1) gauge field. We consider the case with spatially random Kondo exchange, as this leads to strange metal behavior in electrical transport. We find a large asymmetric thermopower in a 'skewed' marginal Fermi liquid, with similarities to the skewed non-Fermi liquid of Georges and Mravlje (arXiv:2102.13224). Our findings are consistent with recent observations in heavy fermion compounds (Z.-Y. Cao et al., arXiv:2408.13604), and describe an enhancement of thermopower on the large Fermi surface side as well as a non-monotonic behavior on the small Fermi surface side. Our results also apply to single-band Hubbard models and the pseudogap transition in the cuprates. In the ancilla framework, single-band models exhibit an inverted Kondo lattice transition: the small Fermi surface pseudogap state corresponds to the condensed Higgs state. This inversion results in an enhancement of thermopower on the pseudogap side in our theory, consistent with observations in the cuprates (C. Collignon et al., arXiv:2011.14927; A. Gourgout et al., arXiv:2106.05959). We argue that these observations support a non-symmetry-breaking Fermi-volume-changing transition as the underlying description of the onset of the pseudogap in the cuprates.