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Pressure induced suppression of the singlet insulator phase in BaVS$_3$: infrared optical study

I. Kézsmárki·G. Mihály·R. Gaál·N. Barišić·H. Berger·L. Forró·C. C. Homes·L. Mihály
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Abstract

The metal-insulator (MI) transition in BaVS$_3$ has been studied at ambient pressure and under hydrostatic pressure up to $p=26 $kbar in the frequency range of $20-3000 $cm$^{-1}$. The charge gap determined from the optical reflectivity is enhanced, $Δ_{ch}(p)/k_BT_{MI}(p)\sim 12$. This ratio is independent of pressure indicating that the character of the transition does not vary along the $p-T$ phase boundary. Above the critical pressure, $p_{cr}\sim20$ kbar, metallic spectra were recorded in the whole temperature range, as expected from the shape of the phase diagram. Our results exclude the opening of a pseudogap above $T_{MI}$ at any pressure. Below $T_{MI}$ an unusually strong temperature dependence of the charge gap was observed, resulting in a $Δ_{ch}(T)$ deviating strongly from the mean field-like variation of the structural order parameter.

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I. Kézsmárki, G. Mihály, R. Gaál, N. Barišić, H. Berger, L. Forró, C. C. Homes, L. Mihály. 2003-11-17. Pressure induced suppression of the singlet insulator phase in BaVS$_3$: infrared optical study. https://doi.org/10.1103/physrevb.71.193103

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