2013/07/02 by L. De Sarlo, Luigi De Sarlo, Lingxuan Shao +6 · 2 citations
Physics and Astronomy · #Antiferromagnetism #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Magnetic field #Mesoscopic physics #Physics #Physics of Superconductivity and Magnetism #Quantum many-body systems #Quantum mechanics #Spin (aerodynamics) #Spin states #Zeeman effect #cond-mat.quant-gas
paper · pdf · doi:10.1088/1367-2630/15/11/113039
published as New J. Phys. 15, 113039 (2013) · submitted to NJP
arxiv created 2013/07/02 · openalex publication_date 2013/11/19 · arxiv updated 2014/12/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study spin fragmentation of an antiferromagnetic spin 1 condensate in the presence of a quadratic Zeeman (QZ) effect breaking spin rotational symmetry. We describe how the QZ effect turns a fragmented spin state, with large fluctuations of the Zeeman populations, into a regular polar condensate, where the atoms all condense in the m = 0 state along the field direction. We calculate the average value and variance of the population of the Zeeman state m = 0 to illustrate clearly the crossover from a fragmented to an unfragmented state. The typical width of this crossover is q ∼ k B T / N , where q is the QZ energy, T the spin temperature and N the atom number. This shows that the spin fluctuations are a mesoscopic effect that will not survive in the thermodynamic limit N → ∞ , but are observable for a sufficiently small atom number.