Selected Publications

- Slippage and Boundary Layer Probed in an Almost Ideal Gas by a Nanomechanical Oscillator

M. Defoort et al., Phys. Rev. Lett.**113**, 136101 (2014) - Evidence for the role of normal-state electrons in nanoelectromechanical damping mechanisms at very low temperatures

K.J. Lulla et al., Phys. Rev. Lett.**110**, 177206 (2013) - Phase Diagram of the Topological Superfluid
^{3}He Confined in a Nanoscale Slab Geometry

L.V. Levitin et al., Science**340**, 841-844 (2013) - Energy and angular momentum balance in wall-bounded quantum turbulence at very low temperatures

J.J. Hosio et al., Nature Commun.**4**, 1614 (2013) - Evidence for Helical Nuclear Spin Order in GaAs Quantum Wires

C.P. Scheller et al., Phys. Rev. Lett.**112**, 066801 (2013) - Observation of a roton collective mode in a two-dimensional Fermi liquid

H. Godfrin et al., Nature**483**, 576 (2012) - The Josephson heat interferometer

F. Giazotto, M.J. Martinez-Perez, Nature**492**, 401 (2012)

## Topological superconductivity in ferromagnetic atom chains beyond the deep-impurity regime

*K. Pöyhönen, A. Westström, T. Ojanen*

Recent developments in the search for topological superconductivity have brought lattices of magnetic adatoms on a superconductor into intense focus. In this work we will study ferromagnetic chains of adatoms on superconducting surfaces with Rashba spin-orbit coupling. Generalizing the deep-impurity approach employed extensively in previous works to arbitrary subgap energies, we formulate the theory of the subgap spectrum as a nonlinear matrix eigenvalue problem. We obtain an essentially analytical description of the subgap spectrum, allowing an efficient study of the topological properties. Employing a flat-band Hamiltonian sharing the topological properties of the chain, we evaluate the Z-valued winding number and discover five distinct topological phases. Our results also confirm that the topological band formation does not require the decoupled Shiba energies to be fine-tuned to the gap center. We also study the properties of Majorana bound states in the system.

*physical review b 93 1*

doi:

*10.1103/PhysRevB.93.014517*