Fermi-Surface Reconstruction in ${\mathrm{CeRh}}_{1-x}{\mathrm{Co}}_x{\mathrm{In}}_5$

The evolution of the Fermi surface of ${\mathrm{CeRh}}_{1-x}{\mathrm{Co}}_x{\mathrm{In}}_5$ was studied as a function of Co concentration $x$ via measurements of the de Haas–van Alphen effect. By measuring the angular dependence of quantum oscillation frequencies, we identify a Fermi-surface sheet with $f$-electron character which undergoes an abrupt change in topology as $x$ is varied. Surprisingly, this reconstruction does not occur at the quantum critical concentration $x_c$, where antiferromagnetism is suppressed to $T=0$. Instead we establish that this sudden change occurs well below $x_c$, at the concentration $x\simeq 0.4$, where long-range magnetic order alters its character and superconductivity appears. Across all concentrations, the cyclotron effective mass of this sheet does not diverge, suggesting that critical behavior is not exhibited equally on all parts of the Fermi surface.

Figure 1

Temperature dependence of the $a$-axis resistivity (circles) and specific heat (triangles) for ${\mathrm{CeRh}}_{1-x}{\mathrm{Co}}_x{\mathrm{In}}_5$ with Co concentration $x=0.5$, which shows coexistence of antiferromagnetic and superconducting order.

Figure 2

Fourier spectrum of quantum oscillations observed in ${\mathrm{CeRh}}_{0.50}{\mathrm{Co}}_{0.50}{\mathrm{In}}_5$ with $\overrightarrow{B}\parallel [001]$, obtained from data collected at 10 mK (upper inset). The temperature dependence of the dHvA amplitude for the 4.5 kT orbit is fitted (solid line) in the lower inset to extract the effective mass $m^{*}$.

Figure 3

Rotational dependence of the dHvA frequencies of ${\mathrm{CeRh}}_{1-x}{\mathrm{Co}}_x{\mathrm{In}}_5$ samples compared to reference data (open symbols) for both end members of the series: ${\mathrm{CeRhIn}}_5$ ($x=0$) in the top panel [13], and ${\mathrm{CeCoIn}}_5$ ($x=1$) in the bottom panel [15] (the size of the reference data symbols is normalized to indicate the intensity of a particular orbit in the dHvA spectrum). For all samples we rotate $\overrightarrow{B}$ from [001] ($\theta =0$) into the [100] direction. The graphic in the lower panel identifies the observed orbits on the two heavy Fermi-surface sheets (adapted from Ref. 10).

Figure 4

Panels (a) and (b) present the dHvA frequency with $\overrightarrow{B}\parallel [001]$ and the effective mass evolution, respectively, of the ${\alpha }_3$ orbit in ${\mathrm{CeRh}}_{1-x}{\mathrm{Co}}_x{\mathrm{In}}_5$ as compared to the end members ${\mathrm{CeRhIn}}_5$ [13] and ${\mathrm{CeCoIn}}_5$ [15] (open symbols), showing minimal change through the antiferromagnetic QCP near $x_c\approx 0.80$ (lines are guides to the eye). Panel (c) maps superconducting (circles) and antiferromagnetic (squares) phase transitions deduced from susceptibility and heat capacity measurements [8, 22], with “ICAF” and “CAF” denoting incommensurate and commensurate AFM phases, respectively, deduced from neutron scattering [26, 27]. The pressure evolution of $T_c$ (dash-dotted line) and position of the pressure-induced QCP (dotted line) from Ref. 23 are shown for comparison. The pressure axis is linearly scaled to match the concentration and pressure values where $T_N=T_c$ (i.e., at $x\simeq 0.75$ and $P=1.85\mathrm{GPa}$) [23].