Amorphous topological superconductivity in a Shiba glass

Abstract

Topological states of matter support quantised nondissipative responses and exotic quantum particles that cannot be accessed in common materials. The exceptional properties and application potential of topological materials have triggered a large-scale search for new realisations. Breaking away from the popular trend focusing almost exclusively on crystalline symmetries, we introduce the Shiba glass as a platform for amorphous topological quantum matter. This system consists of an ensemble of randomly distributed magnetic atoms on a superconducting surface. We show that subgap Yu–Shiba–Rusinov states on the magnetic moments form a topological superconducting phase at critical density despite a complete absence of spatial order. Experimental signatures of the amorphous topological state can be obtained by scanning tunnelling microscopy measurements probing the topological edge mode. Our discovery demonstrates the physical feasibility of amorphous topological quantum matter, presenting a concrete route to fabricating new topological systems from nontopological materials with random dopants.

Magnetic-related States and Order Parameter Induced in a Conventional Superconductor by Nonmagnetic Chiral Molecules

“…In both cases above, ferromagnetic ordering is necessary for the magnetic impurities to induce chiral p-wave symmetry. A similar system of magnetic impurities, but lacking magnetic ordering is described as Shiba glass 16 where even at the presence of a no spatial order, a finite net out-of-plane magnetization may induce topological superconductivity and hence circulating edge modes around the random dopants.…”

Toward Realistic Amorphous Topological Insulators

“…These results are in qualitative agreement with other works that study schematic models for amorphous topological insulators. 13,[15][16][17]19 Additionally, to probe the edge conductivity, we calculate the two-terminal electronic transport properties in a nanoribbon geometry, using the Landauer approach. In Fig.…”

Topological superconductor with a large Chern number and a large bulk excitation gap in single-layer graphene

“…Among all the above TSCs, multiple spatially overlapping Majorana modes, which greatly benefit the transport properties, can only coexist in one-dimensional (twodimensional) TSCs belonging to Class BDI [19][20][21][22][23][24][27][28][29][30] (D [31][32][33][34] ) with integer topological invariant. 35 In reality, the one-dimensional TSCs in Class BDI can easily reduce to the ones indexed by Class D with zero or one Majorana mode.…”

“…35 In reality, the one-dimensional TSCs in Class BDI can easily reduce to the ones indexed by Class D with zero or one Majorana mode. [20][21][22][23][24][28][29][30] As for the two-dimensional TSCs in Class D, the number of the Majorana modes or the Chern number is limited upto two. [32][33][34] More Majorana modes or larger Chern numbers are limited by large chemical potential (i.e., very high doping) and an overall much smaller bulk excitation gap than the proximity-induced superconducting gap.…”

“…So far, most studies focus on the effective p-wave superconductors in hybrid systems with conventional s-wave superconductors in proximity to strong topological insulators, 8 semiconductors with strong spin-orbit coupling (SOC), [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] or ferromagnetic atom chains. [26][27][28][29][30][31][32] Some attention has also been paid to the conventional s-wave superconductors coupled to quantum anomalous Hall (QAH) insulators such as topological insulators with magnetic dopants.…”