Abstract
Topological superconductor is attracting growing interest for its potential application to topological quantum computation. The superconducting proximity effect on the topological insulator surface state is one promising way to yield topological superconductivity. The superconductivity realized at the interface between Bi2Te3 and non-superconductor FeTe is one such candidate. Here, to detect the mutual interaction between superconductivity and topological surface state, we investigate nonreciprocal transport; i.e., current-direction dependent resistance, which is sensitive to the broken inversion symmetry of the electronic state. The largely enhanced nonreciprocal phenomenon is detected in the Bi2Te3/FeTe heterostructure associated with the superconducting transition. The emergent nonreciprocal signal at low magnetic fields is attributed to the current-induced modulation of supercurrent density under the in-plane magnetic fields due to the spin-momentum locking. The angular dependence of the signal reveals the symmetry of superconductivity and indicates the existence of another mechanism of nonreciprocal transport at high fields.
Highlights
Topological superconductor is attracting growing interest for its potential application to topological quantum computation
This method works as an alternative to angle-resolved photoemission spectroscopy (ARPES)[13] and scanning tunneling microscope (STM)[14] to discuss the effect of spin splitting via transport measurement
Nonreciprocal transport is observed in non-centrosymmetric superconductors, such as a chiral nanotube[23] and a transition metal dichalcogenide[24], demonstrating that this probe is applicable to inversion symmetry broken superconductors
Summary
The resistance of Bi2Te3/FeTe behaves as parallel conduction of these two materials except for the resistance drop to zero at around Tc0 = 10.7 K (Fig. 1c), indicating the appearance of superconductivity at the interface[25]. The fitting of the temperature dependence of resistivity with the Berezinskii–Kosterlitz–Thouless (BKT) transition[28,29,30] and the jump in the power law of current–voltage characteristics (Supplementary Fig. 2 and Supplementary Note 2) verifies the twodimensional nature of superconductivity[25], where the binding of the vortex–antivortex pairs realizes the zero-resistance state. If the second term is finite, the resistance value depends on the current direction, namely the nonreciprocal transport appears. To see the correspondence between the temperature dependence of Rω and γ value (Fig. 2d, e), we categorize them into three regions: normal, intermediate, and superconducting region.
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