Electric field exfoliation and high-TC superconductivity in field-effect hole-doped hydrogenated diamond (111)

Abstract

We investigate the possible occurrence of field-effect induced superconductivity in the hydrogenated (111) diamond surface by first-principles calculations. By computing the band alignment between bulk diamond and the hydrogenated surface we show that the electric field exfoliates the sample, separating the electronic states at the valence band top from the bulk projected ones. At the hole doping values considered here, ranging from n = 2.84 × 10 13 cm −2 to n = 6 × 10 14 cm −2 , the valence band top is composed of up to three electronic bands hosting holes with different effective masses. These bands resemble those of the undoped surface, but they are heavily modified by the electric field and differ substantially from a rigid doping picture. We calculate superconducting properties by including the effects of charging of the slab and of the electric field on the structural properties, electronic structure, phonon dispersion and electron-phonon coupling. We find that at doping as large as n = 6 × 10 14 cm −2 , the electron-phonon interaction is λ = 0.81 and superconductivity emerges with TC ≈ 29 − 36K. Superconductivity is mostly supported by in-plane diamond phonon vibrations and to a lesser extent by some out-of-plane vibrations. The relevant electronphonon scattering processes involve both intra and interband scattering so that superconductivity is multiband in nature.

Migdal-Eliashberg theory of multi-band high-temperature superconductivity in field-effect-doped hydrogenated (111) diamond

“…In Ref. 31 it was shown that a SC phase transition can be induced in the hydrogenated diamond (111) surface via field-effect doping at a hole concentration of n dop = 6 × 10 14 cm −2 . This was done by performing DFT calculations in the proper field-effect geometry with Quantum ESPRESSO [36][37][38] as described in Ref.…”

“…Previous density functional theory (DFT) simulations 21,[29][30][31] showed that it is possible to induce a SC phase transition in hydrogenated diamond surfaces by hole-doping in the FET configuration. In these studies, the critical temperature T c was estimated using the McMillan/Allen-Dynes 32,33 formula.…”

“…29 and 30 the authors studied the hydrogenated diamond (110) surface, and predicted a SC phase transition at T c ∼ 1 K. In Ref. 31, on the other hand, it was shown that the hydrogenated diamond (111) surface develops multi-band SC with a much higher T c ∼ 30 K. However, the McMillan/Allen-Dynes formula only gives qualitative results: A more accurate estimate of T c necessitates solving the Migdal-Eliashberg (ME) equations instead 34,35 .…”

“…In this work -starting from the results of Ref. 31 -we study the electric-field-induced high-T c SC in the hydrogenated diamond (111) surface via the full self-consistent solution of the ME equations. In particular, we focus on the role of the multi-band Fermi surface on the SC pairing and T c .…”

Theoretical Explanation of Electric Field‐Induced Superconductive Critical Temperature Shifts in Indium Thin Films

“…[24][25][26] In this work, we show instead a theoretical treatment to properly describe the effect of an electrostatic field on the superconductive properties of more complex materials developed in the framework of Eliashberg theory and successfully applied to Pb and MgB 2 . [28,29] Further development of such a theoretical framework and its validation on different classes of superconductive materials are important to suggest a priori experimental conditions (e.g., number of carriers to induce, device thickness, and so on) for an optimal modulation of superconductive properties in the field-effect architecture [30] and quantitatively describe future experimental results.…”