Experimental signatures of emergent quantum electrodynamics in Pr2Hf2O7
Experimental signatures of emergent quantum electrodynamics in Pr2Hf2O7
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Pr2Hf2O7 中涌现量子电动力学的实验特征
DOI：
10.1038/s41567-018-0116-x
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发表时间：
2018
期刊：
影响因子：
19.6
通讯作者：
Fennell Tom
中科院分区：
文献类型：
--
作者：
Sibille Romain;Gauthier Nicolas;Yan Han;Ciomaga Hatnean Monica;Ollivier Jacques;Winn Barry;Filges Uwe;Balakrishnan Geetha;Kenzelmann Michel;Shannon Nic;Fennell Tom
在量子自旋液体中，组成电子自旋的磁矩避开经典的长程有序，形成一种在宏观长度尺度上量子纠缠和相干的奇异态。这些相为量子信息技术中的器件应用提供了有前途的前景，它们的研究可以揭示量子物质中的新物理。量子自旋冰是一个很有吸引力的提议，其中基本基态性质和激发由一个新兴的U（1）格点规范理论描述。这种量子相干态中的准粒子被预测表现得像磁单极子和电单极子，沿着一个扮演人造光子角色的规范玻色子。然而，这种涌现的晶格量子电动力学在实验中被证明是难以捉摸的。在这里，我们报告的稀土烧绿石磁铁Pr 2 Hf 2 O 7的中子散射测量提供了证据的量子自旋冰基态。我们发现一个准弹性结构因子与夹点-签名的经典自旋冰-被部分抑制，预期在量子相干制度的晶格场理论在有限的温度。我们的结果允许与磁光子激发的光的速度的估计。我们还揭示了一个连续的非弹性自旋激发，这类似于预测的分数，拓扑激发的量子自旋冰。这两个特征表明Pr 2 Hf 2 O 7的低能物理可以用涌现量子电动力学来描述。如果得到证实，对量子自旋冰基态的观测将构成三维量子自旋液体的一个具体例子--一种迄今为止主要在低维度下探索的物质状态。
In a quantum spin liquid, the magnetic moments of the constituent electron spins evade classical long-range order to form an exotic state that is quantum entangled and coherent over macroscopic length scales,. Such phases offer promising perspectives for device applications in quantum information technologies, and their study can reveal new physics in quantum matter. Quantum spin ice is an appealing proposal of one such state, in which the fundamental ground state properties and excitations are described by an emergentU(1) lattice gauge theory, , , –. This quantum-coherent regime has quasiparticles that are predicted to behave like magnetic and electric monopoles, along with a gauge boson playing the role of an artificial photon. However, this emergent lattice quantum electrodynamics has proved elusive in experiments. Here we report neutron scattering measurements of the rare-earth pyrochlore magnet Pr2Hf2O7that provide evidence for a quantum spin ice ground state. We find a quasi-elastic structure factor with pinch points—a signature of a classical spin ice—that are partially suppressed, as expected in the quantum-coherent regime of the lattice field theory at finite temperature. Our result allows an estimate for the speed of light associated with magnetic photon excitations. We also reveal a continuum of inelastic spin excitations, which resemble predictions for the fractionalized, topological excitations of a quantum spin ice. Taken together, these two signatures suggest that the low-energy physics of Pr2Hf2O7can be described by emergent quantum electrodynamics. If confirmed, the observation of a quantum spin ice ground state would constitute a concrete example of a three-dimensional quantum spin liquid—a topical state of matter that has so far mostly been explored in lower dimensionalities.