Thermodynamic anomaly above the superconducting critical temperature in the quasi-one-dimensional superconductor ${\mathrm{Ta}}_4{\mathrm{Pd}}_3{\mathrm{Te}}_{16}$

We study the intrinsic electronic anisotropy and fermiology of the quasi-one-dimensional superconductor ${\mathrm{Ta}}_4{\mathrm{Pd}}_3{\mathrm{Te}}_{16}$. Below $T^{*}=20$ K, we detect a thermodynamic phase transition that predominantly affects the conductivity perpendicular to the quasi-one-dimensional chains. The transition relates to the presence of charge order that precedes superconductivity. Remarkably, the Fermi surface pockets detected by de Haas–van Alphen oscillations are unaffected by this transition, suggesting that the ordered state does not break any translational symmetries but rather alters the scattering of the quasiparticles themselves.

Figure 1

(a) Crystal structure of TPT with the conventional unit cell (dotted) in the representation C2/m. (b) Scanning electron microscope image of a transport device prepared by FIB etching. Red and yellow arrows highlight the $b$ and $a^{*}$ directions, respectively.

Figure 2

(a),(b) Resistivity along the $a^{*}$ and $b$ axes for device FIBab and along the $b$ and $c$ axes for device FIBcb plotted against temperature; the gray dotted line highlights the anomaly at $T^{*}$. (c) Resistivity anisotropy ${\rho }_i/{\rho }_b$ for each device, with $i=a^{*},c$.

Figure 3

(a) Resistivity (normalized by its value at $T=6$ K) along all three crystal axes ($a^{*}, b$, and $c$) plotted against temperature; the gray dotted vertical line marks $T^{*}$ (see text). Inset: temperature dependence of the $a^{*}$ resistivity in a constant magnetic field up to 16 T applied parallel to $c$. (b) Derivatives of the resistivity, $d{\rho }_i/dT$, for each transport direction, with $i=a^{*},b,c$. (c) Temperature dependence of the magnetic susceptibility ${\chi }_v$ for a small number of TPT coaligned single crystals (upper panel) and a separated single crystal (lower panel), oriented with the $b$ axis parallel to the applied magnetic field; insets show closeup of background-subtracted high-field data. Note that $T^{*}$ marks the temperature below which both resistivity and magnetization show a clear feature indicative of a thermodynamic phase transition; the anomalous temperature region is highlighted by the gray shaded area.

Figure 4

(a) Background-subtracted dHvA oscillation data for various field orientations recorded at $T=1.5$ K in the 45 T hybrid magnet. $\theta =0^{\circ }$ corresponds to the applied field along the $c$ axis. (b),(c) Frequency values obtained from fast Fourier transform (FFT) of the data in (a). The field ranges from 25–45 T (black spheres) and 5.5–16 T (green diamonds). (d) Fermi surfaces for unshifted and shifted chemical potential with $\mathrm{\Delta }=0$ and $-27$ meV, respectively. (e) DFT-calculated dHvA oscillation frequencies originating from the $\alpha$ and $\delta$ bands of the Fermi surfaces shown in (d).

Figure 5

(a) Background-subtracted de Haas–van Alphen oscillations measured with a piezoresistive torque magnetometer in a dc 16 T magnet for various temperatures, with $\theta ={10}^{\circ }$ in the upper panel and $\theta ={65}^{\circ }$ in the lower. (b) FFT of the data shown in (a) over a field window of 5.5–15 T. The inset shows FFT data for $B=10–15$ T. (c) Effective mass plots. Solid lines are fits according to Lifshitz-Kosevich theory (see main text).