标题： 从固定点湮灭的连续序到序量子相变 显示英文标题

标题： Continuous order-to-order quantum phase transitions from fixed-point annihilation

摘要： 相变理论中朗道-金兹堡-威尔逊范式之外的一个核心概念是 fractionalization（碎片化）：新准粒子的形成并通过涌现规范场相互作用。这一概念已在不同秩序之间连续量子相变的背景下得到了广泛探索，这些相变打破了不同的对称性。我们提出了一种独立于 fractionalization（碎片化）的连续秩序到秩序量子相变机制。该机制基于两个重正化群不动点的碰撞和湮灭：一个量子临界不动点和一个红外稳定不动点。这两个不动点的湮灭重新排列了流形拓扑结构，消除了与红外稳定不动点相关的无序相，并将不受碰撞影响的第二个临界不动点提升为不同秩序之间的量子临界点。我们认为这一机制适用于广泛的物理系统。特别是，它可以在三维空间中的 Luttinger 费米子系统中表现出来，导致反铁磁 Weyl 半金属态（破坏时间反转对称性）与一种具有晶格旋转对称性破缺特征的各向异性拓扑绝缘体之间的连续量子相变。这种连续的反铁磁-Weyl 到各向异性绝缘体转变可能在稀土石榴石铱化合物$R_2$Ir$_2$O$_7$中被观测到。其他可能的实现包括 Kagome 量子磁体、量子杂质模型以及具有附加四费米子相互作用的量子色动力学。 显示英文摘要

摘要： A central concept in the theory of phase transitions beyond the Landau-Ginzburg-Wilson paradigm is fractionalization: the formation of new quasiparticles that interact via emergent gauge fields. This concept has been extensively explored in the context of continuous quantum phase transitions between distinct orders that break different symmetries. We propose a mechanism for continuous order-to-order quantum phase transitions that operates independently of fractionalization. This mechanism is based on the collision and annihilation of two renormalization group fixed points: a quantum critical fixed point and an infrared stable fixed point. The annihilation of these fixed points rearranges the flow topology, eliminating the disordered phase associated with the infrared stable fixed point and promoting a second critical fixed point, unaffected by the collision, to a quantum critical point between distinct orders. We argue that this mechanism is relevant to a broad spectrum of physical systems. In particular, it can manifest in Luttinger fermion systems in three spatial dimensions, leading to a continuous quantum phase transition between an antiferromagnetic Weyl semimetal state, which breaks time-reversal symmetry, and a nematic topological insulator, characterized by broken lattice rotational symmetry. This continuous antiferromagnetic-Weyl-to-nematic-insulator transition might be observed in rare-earth pyrochlore iridates $R_2$Ir$_2$O$_7$. Other possible realizations include kagome quantum magnets, quantum impurity models, and quantum chromodynamics with supplemental four-fermion interactions.