The ground-state properties and excitation energies of a quantum emitter can be modified in the ultrastrong coupling regime of cavity quantum electrodynamics (QED) where the light-matter interaction strength becomes comparable to the cavity resonance frequency. Recent studies have started to explore the possibility of controlling an electronic material by embedding it in a cavity that confines electromagnetic fields in deep subwavelength scales. Currently, there is a strong interest in realizing ultrastrong-coupling cavity QED in the terahertz (THz) part of the spectrum, since most of the elementary excitations of quantum materials are in this frequency range. We propose and discuss a promising platform to achieve this goal based on a two-dimensional electronic material encapsulated by a planar cavity consisting of ultrathin polar van der Waals crystals. As a concrete setup, we show that nanometer-thick hexagonal boron nitride layers should allow one to reach the ultrastrong coupling regime for single-electron cyclotron resonance in a bilayer graphene. The proposed cavity platform can be realized by a wide variety of thin dielectric materials with hyperbolic dispersions. Consequently, van der Waals heterostructures hold the promise of becoming a versatile playground for exploring the ultrastrong-coupling physics of cavity QED materials.

中文翻译：

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双曲范德瓦尔斯材料的腔量子电动力学

量子发射器的基态特性和激发能量可以在腔量子电动力学 (QED) 的超强耦合状态下进行修改，其中光-物质相互作用强度变得与腔共振频率相当。最近的研究已经开始探索通过将电子材料嵌入一个将电磁场限制在深亚波长范围内的空腔来控制电子材料的可能性。目前，人们对在频谱的太赫兹 (THz) 部分实现超强耦合腔 QED 有着浓厚的兴趣，因为大多数量子材料的基本激发都在这个频率范围内。我们提出并讨论了一个有前途的平台来实现这一目标，该平台基于由超薄极性范德华晶体组成的平面腔封装的二维电子材料。作为一个具体的设置，我们表明纳米厚的六方氮化硼层应该允许人们在双层石墨烯中达到单电子回旋共振的超强耦合状态。所提出的腔体平台可以通过多种具有双曲线色散的薄介电材料来实现。因此，范德瓦尔斯异质结构有望成为探索空腔 QED 材料超强耦合物理学的多功能场所。我们表明，纳米厚的六方氮化硼层应该允许人们在双层石墨烯中达到单电子回旋共振的超强耦合状态。所提出的腔体平台可以通过多种具有双曲线色散的薄介电材料来实现。因此，范德瓦尔斯异质结构有望成为探索空腔 QED 材料超强耦合物理学的多功能平台。我们表明，纳米厚的六方氮化硼层应该允许人们在双层石墨烯中达到单电子回旋共振的超强耦合状态。所提出的腔体平台可以通过多种具有双曲线色散的薄介电材料来实现。因此，范德瓦尔斯异质结构有望成为探索空腔 QED 材料超强耦合物理学的多功能场所。