Superconductivity in the ferromagnetic semiconductor samarium nitride

Abstract

Conventional wisdom expects that making semiconductors ferromagnetic requires doping with magnetic ions, and that superconductivity cannot coexist with magnetism. However, recent concerted efforts exploring new classes of materials have established that intrinsic ferromagnetic semiconductors exist and that certain types of strongly correlated metals can be ferromagnetic and superconducting at the same time. Here we show that the trifecta of semiconducting behavior, ferromagnetism and superconductivity can be achieved in a single material. Samarium nitride (SmN) is a well-characterised intrinsic ferromagnetic semiconductor, hosting strongly spin-ordered 4f electrons below a Curie temperature of 27 K. We have now observed that it also hosts a superconducting phase below 4 K when doped to electron concentrations above 10 21 cm −3 . The large exchange splitting of the conduction band in SmN favors equal-spin triplet pairing with p-wave symmetry. An analysis of the robustness of such a superconducting phase against disorder leads to the conclusion that the 4f bands are crucial for superconductivity, making SmN a heavy-fermion-type superconductor.

Carrier-controlled anomalous Hall effect in an intrinsic ferromagnetic semiconductor

“…9 Their wide-ranging magnetic and coupled magnetic-electronic responses have seen them included in a number of device structures. [10][11][12][13] The series includes at least one supercon- ducting member, 14 and ab initio calculations support the suggestion that they may show both ferroelectric 15 and topological insulator 16 phases. GdN lies in the center of the series with a purely spin magnetic moment of 7 Bohr magnetons (µ B ) per primitive cell that is sited primarily in the Gd 3+ 4f shell.…”

Coexisting structural phases in the catalytically driven growth of rock salt GdN

“…Most of the RENs are narrow bandgap semiconductors, with strongly contrasting magnetic properties from the coupled spin and orbital moments residing in the rare-earth 4f shells, and Curie temperatures typically below 50-70 K [1]. Equally interesting, but unexpected until recent experimental observations and computational treatments, are (i) the key signature of superconductivity in the ferromagnetic semiconductor samarium nitride (SmN) [6], (ii) nearly triple nodal point topological phase [7] and (iii) Chern insulating state in gadolinium nitride (GdN) [8] opening new avenues of investigations. Within the context of device applications, there has been a particular interest in using the RENs in hybrid structures, i.e.…”

p-wave superconductivity in iron-based superconductors

“…Sr 2 RuO 4 is one of the rare materials in which, for two decades now, p -wave superconductivity was thought to exist 3 , but recent experiments 4 suggest that it is in all likelihood a d -wave superconductor. Thus, there is an on-going experimental search for p -wave pairing in new materials 5,6 , including induced superconductivity in graphene-based systems 7 . The current status of the search for p -wave pairing was recently reviewed in 8,9 .…”