Gianluca Bertaina — Università di Milano #
Density fluctuations spectrum of one-dimensional liquid \(^4\)He beyond low-energy Luttinger theory #
We investigate zero temperature liquid \(^4\)He in strictly one dimension by means of state-of-the-art 
Quantum Monte Carlo and analytic continuation techniques [1]. <br/>
The system displays the unique feature of spanning all the possible values of the Luttinger liquid parameter \(K_L\) by 
only changing the density. <br/>
We explore the behavior of the dynamical structure factor \(S(q,\omega)\) beyond the limits of applicability of 
Luttinger liquid theory in the whole range in \(K_L\).
We observe a crossover from a weakly interacting Bose gas regime at low density (\(K_L\gg 1\)) to a quasi-solid regime at 
high density (\(K_L\ll 1\)), which we interpret in terms of novel analytical expressions for the spectrum of hard-rods.
During this transition the interplay between dimensionality and interaction makes \(S(q,\omega)\) manifest a pseudo 
<i>particle-hole</i> continuum typical of a fermionic system, while the Bogoliubov mode evolves into a remnant of the 
roton mode.
We provide also a perturbative estimation of the drag force experienced by a soft impurity moving along the system.
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References<br/>
[1] G. Bertaina, M. Motta, M. Rossi, E. Vitali, and D.E. Galli, arXiv:1412.7179 (2014).