Qiang Yihua, Quito Victor L, Trevisan Thaís V, Orth Peter P
Department of Physics and Astronomy, <a href="https://ror.org/04rswrd78">Iowa State University</a>, Ames, Iowa 50011, USA.
<a href="https://ror.org/041m9xr71">Ames National Laboratory</a>, Ames, Iowa 50011, USA.
Phys Rev Lett. 2024 Sep 20;133(12):126505. doi: 10.1103/PhysRevLett.133.126505.
Two-dimensional coherent terahertz spectroscopy (2DCS) emerges as a valuable tool to probe the nature, couplings, and lifetimes of excitations in quantum materials. It thus promises to identify unique signatures of spin liquid states in quantum magnets by directly probing properties of their exotic fractionalized excitations. Here, we calculate the second-order 2DCS of the Kitaev honeycomb model and demonstrate that distinct spin liquid fingerprints appear already in this lowest-order nonlinear response χ_{yzx}^{(2)}(ω_{1},ω_{2}) when using crossed light polarizations. We further relate the off-diagonal 2DCS peaks to the localized nature of the matter Majorana excitations trapped by Z_{2} flux excitations and show that 2DCS thus directly probes the inverse participation ratio of Majorana wave functions. By providing experimentally observable features of spin liquid states in the 2D spectrum, our Letter can guide future 2DCS experiments on Kitaev magnets.
二维相干太赫兹光谱学（2DCS）成为探测量子材料中激发的性质、耦合和寿命的一种有价值的工具。因此，它有望通过直接探测其奇异的分数化激发的性质来识别量子磁体中自旋液体态的独特特征。在此，我们计算了Kitaev蜂窝模型的二阶2DCS，并证明当使用交叉光偏振时，在这种最低阶非线性响应χ_{yzx}^{(2)}(ω_{1},ω_{2})中已经出现了不同的自旋液体指纹。我们进一步将非对角2DCS峰与被Z_{2}磁通激发捕获的马约拉纳激发的局域性质联系起来，并表明2DCS因此直接探测了马约拉纳波函数的逆参与率。通过在二维光谱中提供自旋液体态的实验可观测特征，我们的信件可以指导未来对Kitaev磁体的2DCS实验。
