Breaking an electron: Spin incoherent behavior in strongly correlated low dimensional systems

Adrian Feiguin, Northeastern University

Electrons are fundamental building blocks of nature and are indivisible in isolation. However, when electrons (or other quantum particles with an internal ``spin" degree of freedom) are confined in one spatial dimension, they loose their identity as individual particles, and ``break'' into separate excitations carrying spin, and charge, with each degree of freedom being characterized by a different energy scale. While the basic theoretical understanding of spin-charge separation in one-dimension, known as ``Luttinger liquid theory'', has existed for some time, recently a previously unidentified regime of strongly interacting one-dimensional systems at finite temperature came to light: The ``spin-incoherent Luttinger liquid". This occurs when the temperature is larger than the characteristic spin energy scale. The key to establishing both Luttinger liquid behavior and spin-incoherent Luttinger liquid behavior in experiment is detailed knowledge of the spectral properties.

I will present a numerical study of the finite-temperature spectral properties of a one-dimensional fermionic gas in the spin-incoherent regime using the time-dependent density matrix renormalization group method. This approach enables us to quantitatively handle the experimentally relevant and theoretically challenging "crossover" regime between the Luttinger liquid and spin-incoherent Luttinger liquid limits. I will discuss the possibility of observing spin-incoherent behavior in spin ladders, in the context of a recent neutron scattering experiment. Finally, I will show that spin-incoherent behavior can be realized in the ground-state of model Hamiltonians, such as Hubbard ladders, and the Kondo lattice.