Majorana Kramers Pairs in Higher-Order Topological Insulators

Abstract

We propose a tune-free scheme to realize Kramers pairs of Majorana bound states in recently discovered higher-order topological insulators (HOTIs). We show that, by bringing two hinges of a HOTI into the proximity of an s-wave superconductor, the competition between local and crossed Andreev pairing leads to the formation of Majorana Kramers pairs, when the latter pairing dominates over the former. We demonstrate that such a topological superconductivity is stabilized by moderate electron-electron interactions. The proposed setup avoids the application of a magnetic field or local voltage gates, and requires weaker interactions compared with nonhelical nanowires.

Majorana Corner Modes with Solitons in an Attractive Hubbard-Hofstadter Model of Cold Atom Optical Lattices

“…Excitations in these systems come in the form of MKPs, which are distinct from non-degenerate MZMs [16][17][18][19][20][21][22][23][24][25][26] and are protected by time reversal (TR) symmetry [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Unfortunately, MCMs proposed in the condensed matter systems [13][14][15][47][48][49][50][51] have not been realized to date.…”

Detection of second-order topological superconductors by Josephson junctions

“…(5). Strikingly, increasing µ R further, we observe a clear 0-π transition for the parameters satisfying inequality (8). While J s (φ) in the region 0 < φ < π is positive for µ R < µ c , it becomes negative for µ R > µ c .…”

“…It is likely realized in the inverted InAs/GaSb bilayer [71][72][73], WTe 2 monolayer [44][45][46][47][48], functionalized MXene [49,50], Bismuthene on SiC [51,52], PbS monolayer [53][54][55], etc. To test the analytical results, we discretize the model (1), put it on a lattice, choose a proper set of parameters (satisfying inequality (8)) and calculate the energy spectrum in a ribbon geometry. For concreteness, we consider ∆ 0 = 0 and set the lattice constant a to unity.…”

“…Introduction.-The second-order topological superconductor (SOTS) is a novel topological phase of matter and features Majorana zero-dimensional (0D) corner or 1D hinge states which are two dimensions lower than the gapped bulk [1][2][3][4][5][6][7][8][9][10][11][12] and may provide stable qubits for topological quantum computation [13][14][15][16][17][18][19][20][21]. Recently, the SOTS has been discovered in a variety of realistic materials and triggered tremendous interest [3][4][5][6][7][8][9][10][22][23][24][25][26][27]. One way to mimic SOTSs in 2D is given by quantum spin Hall insulators (QSHIs) in proximity to unconventional superconductors with d x 2 −y 2 -wave or s ± -wave pairing order [3][4][5].…”

Majorana corner flat bands in two-dimensional second-order topological superconductors

“…In second-order TSCs these MZMs have been studied at the corners of a two-dimensional (2D) system and hinges of a three-dimensional (3D) system where neighboring hinges have different chiralities 27,28 . These zero-energy corner modes are known as Majorana corner states (MCSs) which have been studied in various kinds of system such as high-temperature superconductors (SCs) [29][30][31][32][33][34] , s-wave superfluid 28,35 , systems with an external magnetic field [36][37][38] , and 2D and 3D second-order TSCs 39 .…”