Experimental electronic structure and Fermi-surface instability of the correlated $3d$ sulphide $\mathrm{Ba}\mathrm{V}{\mathrm{S}}_3$: High-resolution angle-resolved photoemission spectroscopy

The correlated $3d$ sulphide $\mathrm{Ba}\mathrm{V}{\mathrm{S}}_3$ exhibits an interesting coexistence of one-dimensional and three-dimensional properties. Our experiments determine the electronic band structure and shed light on this puzzle. High-resolution angle-resolved photoemission measurements in a $4\text{−}\mathrm{eV}$-wide range below the Fermi energy level uncover and investigate the coexistence of $a_{1g}$ wide-band and $e_g$ narrow-band $d$ electrons, which lead to the complicated electronic properties of this material. We explore the effects of strong correlations and the Fermi surface instability associated with the metal-insulator transition.

Figure 1

(Color online) Left: ARPES intensity map at $40\mathrm{K}$ taken in the direction parallel to the structural chains. Brighter color signifies higher intensity. The spectra were normalized and a background was subtracted to enhance the features. Right: the corresponding theoretical LDA band dispersion, adopted from Ref. 10.

Figure 2

(Color online) (a) An MDC of an integrated energy region $E_F<E_B^{*}<50\mathrm{meV}$ from an ARPES map at $150\mathrm{K}$. A double-Lorentzian fit determines the position of $k_{F_1}$ from both sides of the BZ. Below is the equivalent MDC plot taken from a map at $40\mathrm{K}$ and $80\mathrm{meV}$ higher in binding energy to account for the gap opening (Ref. 14). The arrows indicate the positions of the second $E_F$ crossing, $k_{F_2}$. (b) $-d^{2}I∕d{E}^2$ plot of the ARPES map at $40\mathrm{K}$. The white dashed and dotted lines guide the eye in following the dispersions. Refer to the text for details. (c) Selected raw EDCs in equidistant steps from the $\Gamma$ to $Z$ point, plotted with an offset.

Figure 3

Left: EDCs at $k=k_{F_1}$ taken at 140 and $45\mathrm{K}$. The charge gap is observable in the shift of the leading edge, where the actual quasiparticle is situated. Right: the shift of the leading edge as a function of temperature. The dashed line in (right) marks the MIT temperature.