Spin-spin correlations of the spin-ladder compound (C\(_5\)H\(_{12}\)N)\(_2\)CuBr\(_4\) measured by magnetostriction and comparison to Quantum Monte Carlo results

Magnetostriction and thermal expansion of the spin-ladder compound piperidinium copper bromide (C\(_5\)H\(_{12}\)N)\(_2\)CuBr\(_4\) 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...

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Bibliographic Details
Published in:arXiv.org 2008-03
Main Authors: Anfuso, Fabrizio, Garst, Markus, Rosch, Achim, Heyer, Oliver, Lorenz, Thomas, Ruegg, Christian, Kraemer, Karl
Format: Article
Language:English
Subjects:
Computer simulation
Copper bromide
Copper compounds
Couplings
Critical field (superconductivity)
Crystallography
Fermions
Ladder compounds
Magnetic fields
Magnetic permeability
Magnetostriction
Modulus of elasticity
Singularities
Thermal expansion
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Summary:Magnetostriction and thermal expansion of the spin-ladder compound piperidinium copper bromide (C\(_5\)H\(_{12}\)N)\(_2\)CuBr\(_4\) 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 (C\(_5\)H\(_{12}\)N)\(_2\)CuBr\(_4\). We especially focus on the quantum critical behavior near the two critical magnetic fields \(H_{c1}\) and \(H_{c2}\), 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 \(H_{c2}\) is quantitatively described by a parameter-free theory of one-dimensional, non-relativistic 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 \(\chi\) which diverges as \(\chi \sim 1/\sqrt{T}\) at the critical fields and thus leads to a strong softening of the crystal.
ISSN:2331-8422
DOI:10.48550/arxiv.0803.1072