Pressure-induced superconductivity in topological insulator Ge2Bi2Te5 and the evolution with Mn doping

TL;DR

This work investigates how pressure can induce superconductivity in the topological insulator Ge$_2$Bi$_2$Te$_5$ and how Mn doping modifies this behavior. Using high-pressure transport measurements on Ge$_2$Bi$_2$Te$_5$ and (Ge$_{1-x}$Mn$_x$)$_2$Bi$_2$Te$_5$ ($x=0.25,0.49$), the authors observe a dome-shaped $T_c(P)$ in the parent compound, with a maximum $T_c \approx 7.6$ K at $P \approx 23$ GPa, and document a suppressed superconducting state in Mn-doped samples due to emergent antiferromagnetism (with $T_N$ up to $11.8$ K). The upper critical fields follow an orbital-depairing-driven behavior, and Mn doping narrows or eliminates the superconducting region under pressure, signaling a competition between AFM order and superconductivity. Overall, the study reveals a robust interplay between band topology, magnetism, and superconductivity in the $mAX \cdot nB_2X_3$ family, offering a platform to explore topological superconductivity and correlated states.

Abstract

Introducing superconductivity (SC) or magnetism into topological insulators (TIs) can give rise to novel quantum states and exotic physical phenomena. Here, we report a high-pressure transport study on the TI Ge2Bi2Te5 and its Mn-doped counterparts. The application of pressure induces a SC in Ge2Bi2Te5, which shows a dome-shape phase diagram with the maximum Tc of 7.6 K at 23 GPa. Doping Mn into Ge2Bi2Te5 introduces an antiferromagnetic order at ambient pressure and strongly weakens the pressure-induced SC, demonstrating that magnetism and SC compete in this material system. Present study provides a new platform for investigating the interplay among band topology, magnetism, and SC.

Figures (4)

• Figure 1: (a) Structure of (Ge$_{1-x}$Mn$_x$)Bi$_2$Te$_5$ single crystal. The red, blue, green and orange balls represent Ge, Mn, Bi and Te atoms, respectively. (b) Single-crystal XRD patterns of (Ge$_{1-x}$Mn$_x$)$_2$Bi$_2$Te$_5$ single crystals. The left inset shows the enlarged part of (009) peaks. The right inset presents the fitted $c$-axial lattice parameter as a function of $x$. (c) Temperature dependence of $\chi_{c}(T)$ for (Ge$_{1-x}$Mn$_x$)$_2$Bi$_2$Te$_5$ single crystals under 0.1 T with ZFC and FC modes. The curves of Ge$_2$Bi$_2$Te$_5$ are magnified by a factor of 20 for clarity. (d) Normalized resistivity $\rho_{xx}(T)/\rho_{xx}$(2 K) as a function of temperature for (Ge$_{1-x}$Mn$_x$)$_2$Bi$_2$Te$_5$ single crystals.
• Figure 2: (a) Temperature dependence of resistivity $\rho(T)$ at pressures ranging from 0.7 to 57.8 GPa in Ge$_{2}$Bi$_{2}$Te$_{5}$ ($x$ = 0, sample 1). (b) The enlarged $\rho(T)$ curves below 10 K. (c) The $\rho(T)$ as a function of temperature under various magnetic fields at 28.9 GPa. (d) The temperature dependence of $\mu_{0}H_{c2}(T)$ at 18.5, 28.9 and 40.1 GPa, respectively. The solid lines represent the fitting results using the equation $\mu_{0} H_{c2}(T) = \mu_{0} H_{c2}(0)(1-(T/T_{c}))^{1+\alpha}$.
• Figure 3: (a) and (b) Temperature dependence of $\rho(T)$ under pressures up to 61.5 GPa for $x$ = 0.25 sample. The inset of (b) shows the enlarged $\rho(T)$ curves from 1.8 to 4 K. (c) and (d) The $\rho(T)$ curves in the pressure range from 1.6 to 65.3 GPa for $x$ = 0.49 sample.
• Figure 4: Electronic phase diagram of (Ge$_{1-x}$Mn$_{x}$)$_2$Bi$_2$Te$_5$ ($x$ = 0, 0.25 and 0.49).