AI 中文总结
本研究提出利用NV中心磁强计测量$S_z=±1$三重态暗激子BEC的 stray 磁场噪声，通过外磁场调谐可将其自旋声子模式纳入NV检测的吉赫兹范围，为明确识别激子BEC提供了新方法。
AI 中文摘要
激子为实现固态玻色-爱因斯坦凝聚（BEC）提供了极具前景的平台，可展现量子相干性、强关联电子-空穴物理及超流性，但其明确的实验识别仍具挑战性。其中，$S_z=±1$三重态激子因固有复合速率受限、寿命长，是实现激子BEC的优异候选体系；但因其光学检测本征禁戒，实验信号仍难以捉摸。本研究表明，$S_z=±1$三重态激子BEC的磁特性会产生 stray 磁场噪声，可通过氮空位（NV）中心磁强计测量。利用外磁场将系统从反铁磁有序调至铁磁有序时，BEC的纵向自旋声子模式软化，使该模式进入NV自旋弛豫率的特征吉赫兹频率范围，从而实现直接检测。此外，由于Beliaev阻尼形式的声子模式色散与阻尼率的立方修正，在距样品的小距离$d$处，我们观测到非常规的紫外标度。通过该方法，我们证实激子BEC的自旋分量为检测激子BEC提供了新途径。
英文摘要
Excitons provide a promising platform for the realization of solid-state Bose-Einstein condensation (BEC), offering quantum coherence, strongly correlated electron-hole physics, and superfluidity. Yet, its unambiguous experimental identification remains challenging. In particular, $S_z= \pm 1$ triplet excitons are excellent candidates to realize an exciton BEC, because of their intrinsically limited recombination rate and thus long lifetimes. However, since their optical detection is inherently forbidden, experimental signatures remain elusive. In this work, we demonstrate that the magnetic nature of a $S_z= \pm 1$ triplet exciton BEC gives rise to stray magnetic field noise, that can be measured using nitrogen-vacancy (NV) center magnetometry. Using an external magnetic field to tune the system from an antiferromagnetic to a ferromagnetic ordering, the longitudinal spin sound mode of the BEC softens, bringing the mode into the characteristic gigahertz frequency range of the NV spin relaxation rate and thus allowing direct detection. Furthermore, we demonstrate an unconventional UV scaling at small distances $d$ from the sample, owing to the cubic corrections to the sound mode dispersion and damping rate in the form of Beliaev damping. Through this approach, we establish that the spin component of exciton BECs offers new approaches to detect exciton BECs.
Comments6+8 pages
