Observation of Two-Magnon Bound States in the Two-Leg Ladders of(Ca,La)14Cu24

Abstract

Phonon-assisted two-magnon absorption is studied in the spin- 1/2 two-leg ladders of (Ca,La)(14)Cu(24)O(41) for E parallel c (legs) and E parallel a (rungs). We verify the theoretically predicted existence of two-magnon singlet bound states, which give rise to peaks at approximately equal to 2140 and 2800 cm(-1). The two-magnon continuum is observed at approximately equal to 4000 cm(-1). Two different theoretical approaches (Jordan-Wigner fermions and perturbation theory) describe the data very well for J parallel approximately equal to 1020-1100 cm(-1), J parallel/J perpendicular approximately equal to 1-1.2. At high energies, the magnetic contribution to sigma(omega) is strikingly similar in the ladders and in the undoped high-T(c) cuprates, which emphasizes the importance of strong quantum fluctuations in the latter.

Phase diagram of the Heisenberg spin ladder with ring exchange

“…In two dimensions one expects that a larger value of K would be required to find analogs of the more exotic ͑ i.e., chiral͒ phases of the model, and thus that these would most likely be detectable, if at all, as excitations. Films of 3 He have been found to offer larger values of K, but these appear both in combination with other multiple-spin-exchange processes and on a more complex lattice geometry which may lead to further topological possibilities for spin configurations. Our results suggest that this restricted-geometry system may provide a very rich spectrum of possible phases, but a considerably more specific analysis would be required.…”

“…A number of experiments conducted in recent years suggest that multiple spin-exchange interactions have a significant role in the quantitative description of the physics of low-dimensional cuprate compounds, and a qualitative one in determining the properties of 3 He adsorbed on graphite surfaces. Inelastic neutron-scattering measurements of the spin-wave spectrum in the two-dimensional ͑2D͒ cuprate system La 2 CuO 4 ͑Ref.…”

Magnetostrictive Néel ordering of the spin-52ladder compound BaMn2OValldor1, Heyer2, Komarek3 et al. 2011Phys. Rev. B211130View full textAdd to dashboardCite

“…Furthermore, due to the low dimensionality of such spin-ladder materials they can act as model systems and connect theory with experiment in e.g. spectroscopy [11][12][13][14] , thermal conductivity 15,16 , and thermodynamics 17,18 . The spinladder structural features are still rare in nature, but are present in the metal oxide BaMn 2 O 3 19 .…”

Thermodynamic properties of highly frustrated quantum spin ladders: Influence of many-particle bound states

“…When magnetic excitations become highly localized in this way, the related phenomenon of bound-state formation appears. In two-leg spin-1/2 ladders with little or no frustration, bound states are present in the spectrum at higher energies [21,22], whereas in strongly frustrated systems they can occur at low energies, particularly close to a quantum phase transition as in the Shastry-Sutherland model [20,23].…”