Momentum-dependent light scattering in a two-dimensional Heisenberg antiferromagnet: Analysis of x-ray scattering data

Abstract

Motivated by the achievements of the X-ray scattering technique, we analyzed the profile of the light scattering intensity R(q, ω) at a finite q in a 2D Heisenberg antiferromagnet. Previous Raman scattering studies at q = 0 identified the two-magnon peak in B1g scattering geometry. We found that the B1g peak disperses downwards at a finite q, and its intensity increases, reaching its maximum at q = q0 = (0, π) and symmetry related points. In addition, the intensity in the A1g geometry becomes non-zero at a finite q, and also displays a two-magnon peak which gains strength and disperses to larger frequencies with increasing q, and reaches its highest intensity at q0. We found that the profile of R(q0, ω) is equivalent in A1g and B1g geometries.Raman scattering is a powerful probe of magnetic and electronic correlations in interacting electron systems. Raman studies of antiferromagnetic parent compounds of the cuprates in early 90's provided the first estimates of the Heisenberg exchange integrals in La 2 CuO 4 and Y B 2 C 3 O 6 . The values of J ∼ 120 − 140meV were extracted from the positions of the B 1g two-magnon peak which, according to the theory, are located at approximately 2.7J [1]. The values of J extracted from the Raman studies were later confirmed by neutron scattering measurements [2].

Observation of a 500 meV Collective Mode inLa2−xSrxCuO4andNd2Hill1, Blumberg2, Kim3 et al. 2008Phys. Rev. Lett.115101241View full textAdd to dashboardCite

“…Because of small interlayer coupling the resulting interlayer two-magnon mode is expected to occur almost at the noninteracting value, which is in agreement with experimental observations. Finally, we note that, motivated by the present experimental work, a number of authors have investigated the magnetic inelastic x-ray scattering cross section [27][28][29][30]. All find qualitative similarities with the symmetries of the present data.…”

“…The two-magnon DOS also has strong peaks at 600 meV at (0, 0) and (, ) [26], which are not seen in our data, possibly due to the effect of RIXS matrix element. In fact, recent calculations suggest that the twomagnon RIXS cross section is zero or greatly reduced for these points [27][28][29][30].…”

Resonant inelastic x-ray scattering studies of elementary excitations

“…Later theoretical work took the approach of extending bimagnon Raman scattering theory (Elliott and Loudon, 1963;Fleury and Loudon, 1968) to finite momentum transfer (Donkov and Chubukov, 2007;Vernay et al, 2007). This approach is in essence non-resonant because it omits the core-hole (and its effect on the valence electrons) from the analysis.…”

Two-magnon excitations in resonant inelastic x-ray scattering studied within spin density wave formalism

“…Therefore, in contrast to neutron scattering, only an even number of magnons can be excited, whereas an odd number of magnons are prohibited to be excited. In fact, excitations with 500 meV energy and characteristic momentum dependence were observed in the Cu K-edge RIXS for La 2 CuO 4 19,20 , and have been identified as two-magnon excitations, based on the agreement with theoretical calculations [21][22][23][24][25] . In those previous theoretical works they adopted Heisenberg spin Hamiltonians and the spin-wave (SW) approximation.…”