Experimental observation of electron-phonon coupling enhancement in Sn nanowires caused by phonon confinement effects

D. P. Lozano, S. Couet, C. Petermann, G. Hamoir, J. K. Jochum, T. Picot, E. Menéndez, K. Houben, V. Joly, V. A. Antohe, Michael Y. Hu, B. M. Leu, A. Alatas, Ayman H. Said, S. Roelants, B. Partoens, M. V. Milošević, F. M. Peeters, L. Piraux, J. Van de Vondel, A. Vantomme, K. Temst, and M. J. Van Bael

Phys. Rev. B 99, 064512 – Published 21 February 2019

Abstract

Reducing the size of a superconductor below its characteristic length scales can either enhance or suppress its critical temperature ( $T_{c}$ ). Depending on the bulk value of the electron-phonon coupling strength, electronic and phonon confinement effects will play different roles in the modification of $T_{c}$ . Experimentally disentangling each contribution has remained a challenge. We have measured both the phonon density of states and $T_{c}$ of Sn nanowires with diameters of 18, 35, and 100 nm in order to quantify the effects of phonon confinement on superconductivity. We observe a shift of the phonon frequency towards the low-energy region and an increase in the electron-phonon coupling constant that can account for the measured increase in $T_{c}$ .

Received 31 January 2018
Revised 11 January 2019

DOI:https://doi.org/10.1103/PhysRevB.99.064512

Physics Subject Headings (PhySH)

BKT transition Electron-phonon coupling Superconducting phase transition

Low-temperature superconductors Nanowires Quantum wires Type-I superconductors

BCS theory Liquid helium cooling X-ray scattering

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

D. P. Lozano¹, S. Couet¹, C. Petermann¹, G. Hamoir², J. K. Jochum³, T. Picot³, E. Menéndez^1,4, K. Houben³, V. Joly¹, V. A. Antohe^2,5, Michael Y. Hu⁶, B. M. Leu^6,7, A. Alatas⁶, Ayman H. Said⁶, S. Roelants⁸, B. Partoens⁸, M. V. Milošević⁸, F. M. Peeters⁸, L. Piraux², J. Van de Vondel³, A. Vantomme¹, K. Temst¹, and M. J. Van Bael³

¹KU Leuven, Instituut voor Kern-en Stralingsfysica, Celestijnenlaan 200 D, 3001 Leuven, Belgium
²Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain, Place Croix du Sud 1, 1348 Louvain-la-Neuve, Belgium
³Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁴Departament de Física, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain
⁵Research and Development Center for Materials and Electronic & Optoelectronic Devices (MDEO), Faculty of Physics, University of Bucharest, Atomistilor str. 405, 077125 Bucharest-Magurele, Romania
⁶Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
⁷Department of Physics, Miami University, Oxford, Ohio 45056, USA
⁸Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium

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Vol. 99, Iss. 6 — 1 February 2019

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