Fermi surface of the superconductor ${\mathrm{BaIr}}_2{\mathrm{P}}_2$

We report on de Haas–van Alphen (dHvA) and band-structure studies of the iridium-pnictide superconductor ${\mathrm{BaIr}}_2{\mathrm{P}}_2$ ($T_c=2.1$ K). The observed dHvA frequencies can be well understood by our band-structure calculations with two bands crossing the Fermi energy leading to a strongly corrugated Fermi-surface cylinder around the X point and a highly evolved, multiconnected Fermi surface extending over the whole Brillouin zone. The experimental effective masses are found to be considerably larger than the calculated band masses suggesting strong many-body interactions. Nevertheless, $T_c$ remains only moderate in ${\mathrm{BaIr}}_2{\mathrm{P}}_2$ contrary to isostructural iron pnictides which probably is related to the largely different Fermi-surface topologies in these materials.

Figure 1

(a) Torque signal of ${\mathrm{BaIr}}_2{\mathrm{P}}_2$ obtained at about 30 mK between 15 and 18 T. The field was rotated by ${63}^{\circ }$ from the $c$ towards the $a$ axis. (b) Oscillating part of the torque signal after background subtraction. (c) Spectrum of the oscillating signal after Fourier transformation with two clearly resolved dHvA frequencies.

Figure 2

Background-subtracted torque signal (inset) and corresponding Fourier transformation (main panel) measured at about 30 mK at the LNCMI in Grenoble. The field was rotated by $8^{\circ }$ from the $c$ towards the $a$ axis.

Figure 3

Angular dependence of the measured (symbols) and calculated (lines) dHvA frequencies. The open symbols were obtained at the HLD in Dresden in magnetic fields up to 18 T and the closed symbols at the LNCMI in Grenoble in fields up to 34 T. The symbol size is a measure of the Fourier-transformation amplitude [23].

Figure 4

Band structure of ${\mathrm{BaIr}}_2{\mathrm{P}}_2$ calculated using the fplo code. Two bands, colored in red and green, are crossing the Fermi energy, set to zero. The inset shows the Brillouin zone with symmetry points.

Figure 5

Calculated Fermi surface of ${\mathrm{BaIr}}_2{\mathrm{P}}_2$ originating from (a) the red and (b) green band crossing the Fermi energy (Fig. 4). Some of the dHvA orbits are depicted by solid lines and labeled.