Modifying the Momentum Distribution of One-Dimensional Spin-Orbit-Coupled Bose Gases

Momentum distribution manifests some properties of a quantum system. For instance, temperature, interparticle interactions and dimensionality can affect the shape of the momentum distribution. We experimentally investigate one-dimensional (1D) spin-orbit-coupled Bose gases, which energy-momentum dispersion and the corresponding momentum distribution are engineered by changing the parameters of the spin-orbit coupling (SOC). The Luttinger liquid theory is usually used to describe the low-energy properties of 1D quantum systems. To go beyond the Luttinger liquid theory, the nonlinear dispersion is an essential feature. SOC provides an alternative method to reach such novel phenomena in 1D quantum systems. We find that the Raman coupling strength around the critical value notably modifies the 1D momentum distribution to an exponential decay form, which goes beyond the power-law-decay prediction of the Luttinger liquid theory.