2014/05/31 by Andreas Kreisel, Michael Peter, Peter Kopietz
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Anisotropy #Antiferromagnetism #Bose gas #Bose–Einstein condensate #Condensed matter physics #Ferromagnetism #Ground state #Light cone #Magnetic and transport properties of perovskites and related materials #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Scattering #Spin (aerodynamics) #Spin wave #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.90.075130
published as Phys. Rev. B 90, 075130 (2014) · 13 pages, 7 figures
openalex publication_date 2014/08/18 · arxiv created 2014/09/04 · arxiv updated 2014/09/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
For temperatures below 0.6 K the geometrically frustrated layered quantum antiferromagnet Cs2CuCl4 in a magnetic field perpendicular to the layers orders magnetically in a so-called cone state where the magnetic moments have a finite component in the field direction, whereas their projection onto the layers forms a spiral. Modeling this system by a two-dimensional spatially anisotropic quantum Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interaction, we find that even for vanishing temperatures the usual spin-wave expansion is plagued by infrared divergencies which are due to the coupling between longitudinal and transverse spin fluctuations in the cone state. Similar divergencies appear also in the ground state of the interacting Bose gas in two and three dimensions. Using known results for the correlation functions of the interacting Bose gas, we present a nonperturbative expression for the dynamic structure factor in the cone state of Cs2CuCl4. We show that in this state the spectral line shape of spin fluctuations exhibits singular scattering continua which can be understood in terms of the well-known anomalous longitudinal fluctuations in the ground state of the two-dimensional Bose gas.