2008/03/07 by Fabrizio Anfuso, Markus Garst, Achim Rosch +8
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Organic and Molecular Conductors Research #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.77.235113
published as Phys. Rev. B 77, 235113 (2008) · 12 pages, 8 figures included
arxiv created 2008/03/07 · openalex publication_date 2008/06/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Magnetostriction and thermal expansion of the spin-ladder compound piperidinium copper bromide (C5H12N)2CuBr4 are analyzed in detail. We find perfect agreement between experiments and the theory of a two-leg spin-ladder Hamiltonian for more than a decade in temperature and in a wide range of magnetic fields. Relating the magnetostriction along different crystallographic directions to two static spin-spin correlation functions, which we compute with quantum Monte Carlo, allows us to reconstruct the magnetoelastic couplings of (C5H12N)2CuBr4. We especially focus on the quantum critical behavior near the two critical magnetic fields Hc1 and Hc2, which is characterized by strong singularities rooted in the low dimensionality of the critical spin system. Extending our discussion in Lorenz [ et al. Phys. Rev. Lett. 100, 067208 (2008)], we show explicitly that the thermal expansion near the upper critical field Hc2 is quantitatively described by a parameter-free theory of one-dimensional, nonrelativistic fermions. We also point out that there exists a singular quantum critical correction to the elastic moduli. This correction is proportional to the magnetic susceptibility \ensuremathχ, which diverges as \ensuremathχ\ensuremath∼1/√(T) at the critical fields and thus leads to a strong softening of the crystal.