Low-lying excitation spectrum of quantum anharmonic crystals

Philippe H. Monthoux, Efstratios Manousakis

Willy Bierter, Harry L. Morrison

Szu-Cheng Cheng

We apply the magneto-roton theory of the fractional quantum Hall effect to study the collective excitation spectrum of rotating dipolar Fermi gases. The predicted spectrum has a finite energy gap in the long wavelength limit and a roton minimum at finite wave vector. The roton minimum being deepened from filling factor 1/3 to filling factor 1/5 is a signature of incipient crystallization near filling factor 1/7. We also demonstrate that there are no low-lying single-particle excitations below the roton mode. The fractional-quantum-Hall fluid rotating dipolar fermions behaves as an incompressible superfluid at low temperature.

Yuri V. Kozitsky

M Van Canneyt, Jacek Wojtkiewicz

In this paper we continue the investigation of the structural phase transition in a quantum anharmonic crystal. We calculate the influence of breaking the symmetry of the interaction potential on the behaviour of fluctuations and their critical exponents. More precisely, it is shown that when the low-momentum asymptotics of the phonon spectrum (i.e. the Fourier transform of the interaction matrix) have a quartic asymptotic in one direction, the critical exponents for the momentum and position fluctuations increase on the critical line. The quantum nature of the fluctuations in T = 0 is, however, preserved.

Nikolai N Rozanov, В. А. Смирнов