Quantum Simulation with Ultra-Cold Atoms: Spin-Charge Separation
Jess McIver (firstname.lastname@example.org) and Georg Rieger (email@example.com)
**All are welcome at this event!**
Location change: Department colloquia have been moved to HENN 201 for this term 2.
We employ quantum simulation of interesting electronic materials using ultracold 6 Li atoms, a composite fermion, as stand-ins for the electrons Quantum simulation of this kind takes advantage of the capability to adhere to a theoretical model, while the tunability of model parameters enables quantitative comparison with theory.
As an example, I will describe interacting spin-1/2 fermions confined to one-dimensional (1D). The low energy excitations are most likely collective in low dimensions, and thus realizes the Luttinger liquid. The low energy excitations are bosonic sound waves that correspond to either spin-density or charge-density waves that, remarkably, propagate at different speeds, thus realizing a spin-charge separation. This phenomena has been observed in electronic materials, but a quantitative analysis has proved challenging because of the complexity of the electronic structure and the unavoidable presence of impurities and defects. In collaboration with our theory colleagues, we made a direct theory/experiment comparison and found excellent agreement as a function of interaction strength . We found that it was necessary to include nonlinear corrections to the spin-wave dispersion arising from back-scattering, thus going beyond the Luttinger model. More recently, we explored the disruption of spin correlations with increasing temperature , an effect that destroys spin-charge separation.
Our experiment uses Bragg spectroscopy to measure the momentum and energy resolved structure factor, S(q,ω), from which the two speeds of sound are determined.
1. R. Senaratne*, D. Cavazos-Cavazos* et al, “Spin-charge separation in a 1D Fermi gas with tunable interactions”, Science 376, 1305 (2022).
2. D. Cavazos-Cavazos, R. Senaratne, A. Kafle, and R.G. Hulet, “Realization of a spin-incoherent Luttinger liquid”, arXiv:2210.06306 (2022).
Randall G. Hulet earned a BS degree at Stanford University and a Ph.D. in Physics at MIT. He was a National Research Council Fellow at the National Institute of Standards and Technology, where he worked on laser cooling of trapped atomic ions. He joined the faculty of Rice University in 1987 and he currently holds the Fayez Sarofim Chair in Natural Sciences. He has received many awards, including the I.I. Rabi Prize and the Davisson-Germer Prize of the American Physical Society, the National Science Foundation Presidential Young Investigators Award, a NASA Medal for Exceptional Scientific Achievement, and the Herbert Walther Award from the European Physical Society and the Optical Society of America. He is a member of the American Academy of Arts and Sciences.
Hulet is known for his many contributions to atomic physics including helping to develop methods for laser cooling and trapping of atoms. His group first realized Bose-Einstein condensation in an atomic gas with attractive interactions, created a degenerate Bose-Fermi mixture, and observed antiferromagnetic order in the Fermi-Hubbard model using ultracold atoms. More recently, his focus has been on interacting fermions and bosons confined to one-
dimension, which has produced detailed explorations of spin-charge separation and matter-wave solitons, respectively.
To view Dr. Hulet's website, please see here.