AV3Sb5 anomalies
\(Av_3Sb_5\) anomalies¶
Tags: #Anomaly
- The \(AV_3Sb_5\) compounds show abrupt changes1 in the magnetic susceptibility and heat capacity around 78 K (A = K), 102 K (A = Rb), and 94 K (A = Cs). They further become superconducting below 0.9 K (A = K and Rb), and 2.5 K (A = Cs).
| Magnetization | Specific Heat |
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- On one hand, the robust nature of the anomaly under magnetic field and absence of local magnetism witnessed by muon spin spectroscopy suggest that mostly charge degrees of freedom should be involved.
- On the other hand, the anomalous Hall effect is strongly enhanced in \(KV_3Sb_5\) and \(CsV_3Sb_5\) below the 78 K (94 K) transition and has been ascribed to scattering from spin clusters.
- Recent STM results on \(KV_3Sb_5\) demonstrate chiral response under reversed magnetic field and also suggest that the low-temperature electronic state may not be a conventional charge order.
- Phonons are instrumental in driving charge-density-wave instabilities via strong momentum dependence of the electron–phonon coupling.
Important
Broadband optical spectroscopy experiments2 suggest electron–phonon and electron–electron interactions, two important ingredients of the \(KV_3Sb_5\) physics.
- At low temperatures, the localization peak in \(CsV_3Sb_5\) shifts to zero energy and merges with the Drude peak, unlike in \(KV_3Sb_5\) where the peak position saturates at finite energies (see ref. 2).
- This indicates that the slowing down of electron dynamics is thermally activated in \(CsV_3Sb_5\), possibly due to interactions with phonons, while in \(KV_3Sb_5\) it is intrinsic to electrons and, therefore, persists even at low temperatures.
Suggests that that electron–electron interactions must play a significant role in \(KV_3Sb_5\), and that it is significantly different from its Cs sibling. These differences may also be responsible for the complete screening of phonons in \(CsV_3Sb_5\), as opposed to \(KV_3Sb_5\).