Evidence for proximity of ${\mathrm{YFe}}_2{\mathrm{Si}}_2$ to a magnetic quantum critical point

Calculations of the electronic and magnetic properties of the nonmagnetic metallic compound ${\mathrm{YFe}}_2{\mathrm{Si}}_2$ are reported. These predict at the density functional level a magnetic state involving ordering along the $c$ axis. This predicted ground state contrasts with experiment, which does not show magnetic order. The electronic structure is three dimensional, and is similar to that of the unconventional superconductor ${\mathrm{YFe}}_2{\mathrm{Ge}}_2$ as well as that of the high-pressure collapsed tetragonal phase of ${\mathrm{KFe}}_2{\mathrm{As}}_2$, which is also a superconductor. Based on the results in relation to experiment, we infer that properties of ${\mathrm{YFe}}_2{\mathrm{Si}}_2$ are strongly influenced by a nearby antiferromagnetic quantum critical point.

Figure 1

Calculated non-spin-polarized band structure of ${\mathrm{YFe}}_2{\mathrm{Si}}_2$.

Figure 2

Calculated electronic density of states and Fe $d$ projection on a per formula unit basis (note that there are two Fe atoms per formula unit).

Figure 3

Bands near the Fermi energy, emphasizing different Fe $d$ orbital characters by fat bands. The coordinate systems for the orbital character is the square lattice defined by the Fe plane, which is rotated ${45}^{\circ }$ from the tetragonal $a$ and $b$ lattice directions for the two Fe atom unit cell.

Figure 4

Fermi surfaces of ${\mathrm{YFe}}_2{\mathrm{Si}}_2$, showing four hole sheets $\left(h1,h2,h3,h4\right)$ and one electron sheet $\left(e1\right)$.

Figure 5

Fixed spin moment energy as a function of constrained spin magnetization shown on a per Fe atom basis. Note that the values given are from the whole unit cell, and are not the values inside the Fe LAPW sphere.

Figure 6

$c$-axis view of the Fermi surface for the non-spin-polarized case, and the $A$-type and $A4$ (see text) orders.

Figure 7

Density of states for non-spin-polarized, the ground-state $A$-type antiferromagnetic state, and the $S3$ state.