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Register a new userComment on Low Temperature Magnetic Instabilities in Triply Charged Fulleride Polymers by D. Arcon et al., PRL 84, 562 (2000)
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Recently, Arcon et al. reported ESR studies of the polymer phase (PP) of Na_{2}Rb_{0.3}Cs_{0.7}C_{60} fulleride. It was claimed that this phase is a quasi-one-dimensional metal above 45 K with a spin-gap below this temperature and has antiferromagnetic(AF) order below 15 K, that is evidenced by antiferromagnetic resonance(AFMR). For the understanding of the rich physics of fullerides it is important to identify the different ground states. ESR has proven to be a useful technique for this purpose. However, since it is a very sensitive probe, it can detect a multitude of spin species and it is not straightforward to identify their origin, especially in a system like Na_{2}Rb_{x}Cs_{1-x}C_{60} with three dopants, when one part of the sample polymerizes but the majority does not. The observation of a low dimensional instability in the single bonded PP would be a novel and important result. Nevertheless, in this Comment we argue that Na_{2}Rb_{0.3}Cs_{0.7}C_{60} is not a good choice for this purpose since, as we show, the samples used by Arcon et al. are inhomogeneous. We point out that recent results on the PP of Na_{2}CsC_{60} contradicts the observation of low dimensional instabilities in Na_{2}Rb_{0.3}Cs_{0.7}C_{60}.
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In a recent letter [D. Poletti et al., EPL 93, 37008 (2011)] a model of attractive spinless fermions on the honeycomb lattice at half filling has been studied by mean-field theory, where distinct homogenous phases at rather large attraction strength $V>3.36$, separated by (topological) phase transitions, have been predicted. In this comment we argue that without additional interactions the ground states in these phases are not stable against phase separation. We determine the onset of phase separation at half filling $V_{ps}approx 1.7$ by means of infinite projected entangled-pair states (iPEPS) and exact diagonalization.
In a comment on arXiv:1006.5070v1, Drechsler et al. present new band-structure calculations suggesting that the frustrated ferromagnetic spin-1/2 chain LiCuVO4 should be described by a strong rather than weak ferromagnetic nearest-neighbor interaction, in contradiction with their previous calculations. In our reply, we show that their new results are at odds with the observed magnetic structure, that their analysis of the static susceptibility neglects important contributions, and that their criticism of the spin-wave analysis of the bound-state dispersion is unfounded. We further show that their new exact diagonalization results reinforce our conclusion on the existence of a four-spinon continuum in LiCuVO4, see Enderle et al., Phys. Rev. Lett. 104 (2010) 237207.
In a comment on arXiv:1006.5070v2, Drechsler et al. claim that the frustrated ferromagnetic spin-1/2 chain LiCuVO4 should be described by a strong rather than weak ferromagnetic nearest-neighbor interaction, in contradiction with their previous work. Their comment is based on DMRG and ED calculations of the magnetization curve and the magnetic excitations. We show that their parameters are at odds with the magnetic susceptibility and the magnetic excitation spectrum, once intensities are taken into account, and that the magnetization curve cannot discriminate between largely different parameter sets within experimental uncertainties. We further show that their new exact diagonalization results support the validity of the RPA-approach, and strongly reinforce our conclusion on the existence of a four-spinon continuum in LiCuVO4, see Enderle et al., Phys. Rev. Lett. 104 (2010) 237207.
Previously, we reported that the doping and pressure dependence of the $T^ast(B)$ crossover in YbRh$_2$Si$_2$ is incompatible with its interpretation as signature of a Kondo breakdown [M.-H. Schubert et al., Phys. Rev. Research 1, 032004(R) (2019)]. The comment by S. Wirth et al. [arXiv:1910.04108] refers to Hall measurements on undoped YbRh$_2$Si$_2$ and criticizes our study as incomplete and inconclusive. We thoroughly inspect these data and rebut the arguments of the comment.
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