Magnetic and phononic dynamics in the two-ladder quantum magnet (C5H9NH3)2CuBr4
Artikel i vetenskaplig tidskrift, 2026
In quantum magnetic materials it is common to observe both static and dynamic lattice effects on the magnetic excitation spectrum. Less common is to find that the magnetic correlations have a significant impact on the phonon spectrum. Here we study the metal-organic material (C5H9NH3)2CuBr4(Cu-CPA), in which an explanation of the low-lying excitations depends crucially on a full understanding of both the spin and lattice subsystems. We report high-resolution neutron spectroscopy enabled by large, deuterated single crystals that reveal how both sectors are affected by the recently discovered structural phase transition. By measuring over several Brillouin zones, we disentangle the vibrational contribution to the spectrum in order to obtain an accurate estimate of the quasi-one-dimensional magnetic signal. The low-energy magnetic excitations are dominated by two gaps, Δb = 0.41 meV and Δa = 0.55 meV, which contribute with equal intensity ratios, confirming that Cu-CPA realizes a two-ladder spin Hamiltonian, and we deduce the magnetic interaction parameters of both ladders. The phonon spectrum contains highly localized modes at an anomalously low energy around 2 meV. For half of these modes, this characteristic frequency drops by approximately 5% as magnetic correlations become established with decreasing temperature, and we connect this apparent “elastomagnetic” behavior with the location and structure of the cyclopentylammonium rings.
Författare
J. Philippe
Paul Scherrer Institut
Universität Zürich
Frank Elson
Kungliga Tekniska Högskolan (KTH)
T. Arh
Paul Scherrer Institut
S. Sanz
Forschungszentrum Jülich
M. Metzelaars
Forschungszentrum Jülich
RWTH Aachen University
D. W. Tam
Kungliga Tekniska Högskolan (KTH)
Ola Kenji Forslund
Universität Zürich
Uppsala universitet
O. Shliakhtun
Universität Zürich
Paul Scherrer Institut
C. Jiang
Kungliga Tekniska Högskolan (KTH)
Jakob Lass
Paul Scherrer Institut
Manh Duc Le
STFC Rutherford Appleton Laboratory
J. Ollivier
Institut Laue-Langevin
P. Bouillot
Université de Genève
T. Giamarchi
Université de Genève
M. Bartkowiak
Paul Scherrer Institut
Daniel G. Mazzone
Paul Scherrer Institut
Paul Kögerler
RWTH Aachen University
Martin Månsson
Kungliga Tekniska Högskolan (KTH)
A. M. Läuchli
Paul Scherrer Institut
Ecole Polytechnique Federale de Lausanne (EPFL)
Yasmine Sassa
Chalmers, Fysik, Materialfysik
Kungliga Tekniska Högskolan (KTH)
Marc Janoschek
Paul Scherrer Institut
Universität Zürich
B. Normand
Paul Scherrer Institut
Gediminas Simutis
Paul Scherrer Institut
Physical Review B
2469-9950 (ISSN) 2469-9969 (eISSN)
Vol. 113 13 134438Ämneskategorier (SSIF 2025)
Den kondenserade materiens fysik
DOI
10.1103/89JZ-CF9Z