Superconducting phase diagram and nontrivial band topology of structurally modulatedSn1−xSbx

Abstract

We report the discovery of superconductivity in binary alloy Sn1−xSbx with x in the range of 0.43 to 0.6, which possesses a modulated rhombohedral structure due to the incommensurate ordering of Sn and Sb layers along the c-axis. The specific heat measurements indicate a weakly coupled, fully gapped superconducting state in this homogeneity range with a maximum bulk Tc of 1.58 K at x = 0.46, though the electronic specific heat and Hall coefficients remain nearly x-independent. The nonmonotonic dependence of the bulk Tc is discussed in relation to the effects of Sb-layer intercalation between the [Sn4Sb3] seven-layer lamellae that are the essential building block for superconductivity. On the other hand, a zero-resistivity transition is found to take place well above the bulk superconducting transition, and the corresponding Tc increases monotonically with x from 2.06 K to 3.29 K. This contrast, together with the uniform elements distribution revealed by energy dispersive x-ray mapping, implies that the resistive transition is due to the strain effect at the grain boundary rather than the compositional inhomogeneity. The first-principles calculations on the representative composition Sn4Sb3 (x = 0.43) indicate that it is topologically nontrivial similar to Sb, but with different Z2 invariants (0;111). Our results not only identify a new superconducting region in the Sn-Sb phase diagram, but also provide a viable platform to study the interplay between structural modulation, nontrivial band topology and superconductivity.

Type-II superconductivity below 4K in Sn0.4Sb0.6

“…DC magnetization measurements exhibited superconductivity below 4K. In an earlier report[15],superconductivity is observed at below 4K for x=0.43, albeit with a relatively broader transition. M-H plots at various temperatures give a clear glimpse of Type-II superconductivity in this material, neglecting the possibility that this enhanced T c may be due to Sn, which is Type-I superconductor with T c near to 3.7K.ExperimentalSn 0.4 Sb 0.6 crystal is synthesized by solid state reaction route via vacuum encapsulation in PID controlled muffle furnace.…”

“…Superconductivity in SnSb is reported a long time ago [17], in a joint report of intermetallic superconductors. The interest renewed once again when recently, it is been predicted from first principal density functional calculations [15] that same may be a TS and a detailed report showing bulk superconductivity in SnSb appeared in 2018 [18]. In a recent study it has been shown that critical temperature can be tuned in SnSb by changing the elemental composition viz Sn 1x Sb x .…”

“…In regards of topological nature of Sn 1-x Sb x , first principles calculation in Ref. 15 shows considerable band opening on inclusion of SOC. It is a known fact that topological properties in materials can be triggered by hetero-structure engineering [19], which involves modification in stacking sequence of atomic layers or insertion of extra atomic layers in unit cell.…”

“…So it is important to study the superconductivity in these topologically non trivial binary alloys. In this context, binary alloy containing Sn and Sb draws the attention as Sb also have topological non trivial surface states [14,15], hence its alloy may show topological behavior. This system of Sn and Sb is structurally different from that of Bi 1-x Sb x in which there is a random distribution of atoms of Bi and Sb in lattice.…”

Excited-state dynamics of structurally characterized crystal of SnxSb1-x

“…type II superconductor below 1.5 K at x=0.5 [26][27][28][29]. Recently, in our previous report, there is an enhancement in the superconducting critical temperature at x=0.4.…”