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Spin-Orbit Coupled One-Dimensional Fermi Gases with Infinite Repulsion

The current efforts of studying many-body effects with spin-orbit coupling (SOC) using alkali-metal atoms are impeded by the heating effects due to spontaneous emission. Here, we show that even for SOCs too weak to cause any heating, dramatic many-body effects can emerge in a one-dimensional(1D) spin 1/2 Fermi gas provided the interaction is sufficiently repulsive. For weak repulsion, the effect of a weak SOC (with strength $Ω$) is perturbative. inducing a weak spin spiral (with magnitude proportional to $Ω$). However, as the repulsion $g$ increases beyond a critical value ($g_c\sim 1/Ω$), the magnitude of the spin spiral rises rapidly to a value of order 1 (independent of $Ω$). Moreover, near $g=+\infty$, the spins of neighboring fermions can interfere destructively due to quantum fluctuations of particle motion, strongly distorting the spin spiral and pulling the spins substantially away from the direction of the local field at various locations. These effects are consequences of the spin-charge separation in the strongly repulsive limit. They will also occur in other 1D quantum gases with higher spins.