The open-shell p-electron compound Cs4O6 features anionic charge ordering with a concomitant jump in electronic conductivity.

Recently it was proposed that the orbital ordering of π *x,y molecular orbitals in the superoxide CsO2 compound leads to the formation of spin-1/2 chains below the structural phase transition occuring at Ts1 = 61 K on cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR) study of this phase in CsO2 powder. The EPR signal appears as a broad line below Ts1, which is replaced by the antiferromagnetic resonance below the Néel temperature TN = 8.3 K. The temperature dependence of the EPR linewidth between Ts1 and TN agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of S = 1/2 spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR lineshape, linewidth and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent K = 0.48. Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO2, which is, therefore, a unique p−orbital system where such a state could be studied.

by Verwey [7,8].Alkali sesquioxides (A 4 O 6 , A = Rb, Cs) are anionic mixed-valence compounds with simple cubic structure at room temperature [ Fig. 1(a)] and electronic states dominantly affected by π-molecular orbitals of O 2 units [9-13]. The four alkali metals donate four electrons to the three O 2 molecules, resulting in their average charge state of O −4/3 2 arXiv:1911.12049v1 [cond-mat.str-el]

Citation for published item: § tefn § i § D ele § s nd uluppD qy¤ ongyi nd un)i § D ilen nd u(tD hmitry F nd v § rD q § sper nd oto § nikD enton nd feeyD endrew nd er § onD henis @PHIUA 9riphenylideEsed moleulr solid" new ndidte for quntum spinEliquid ompoundF9D he journl of physil hemistry gFD IPI @PUAF ppF IRVTREIRVUIFFurther information on publisher's website:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in The journal of physical chemistry C, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see https://doi.org/10.1021/acs.jpcc.7b02763Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

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