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arXiv · 2103.08122

Photon echo from lensing of fractional excitations in Tomonaga-Luttinger spin liquid

Zi-Long Li·Masaki Oshikawa·Yuan Wan
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Abstract

We study theoretically the nonlinear optical response of Tomonaga-Luttinger spin liquid in the context of terahertz (THz) two-dimensional coherent spectroscopy (2DCS). Using the gapless phase of the XXZ-type spin chain as an example, we show that its third-order nonlinear magnetic susceptibilities $\chi^{(3)}_{+--+}$ and $\chi^{(3)}_{-++-}$ exhibit photon echo, where $\pm$ refers to the left/right-hand circular polarization with respect to the $S^z$ axis. The photon echo arises from a ``lensing'' phenomenon in which the wave packets of fractional excitations move apart and then come back toward each other, amounting to a refocusing of the excitations' world lines. Renormalization group irrelevant corrections to the fixed point Hamiltonian result in dispersion and/or damping of the wave packets, which can be sensitively detected by lensing and consequently the photon echo. Our results thus unveil the strength of THz-2DCS in probing the dynamical properties of the collective excitations in a prototypical gapless many-body system.

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Zi-Long Li, Masaki Oshikawa, Yuan Wan. 2021-03-15. Photon echo from lensing of fractional excitations in Tomonaga-Luttinger spin liquid. https://doi.org/10.1103/physrevx.11.031035

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