Pressure-induced superconductivity in Li-Te electrides

Abstract

Electrides, which accommodate excess of electrons in lattice interstitials as anions, usually exhibit interesting properties and broad applications. Until now, most electrides, especially at high pressures, show semiconducting/insulating character arising from the strong localization of interstitial and orbital electrons. However, modulating their connectivity could turn them into metals and even superconductors. In this work, with the aid of first-principles particle swarm optimization, we have identified a series of pressure-induced Li-rich electrides in the Li-Te system, in which hollow Li n polyhedra accommodate the excess of electrons. With increasing Li content, these electrides undergo an interesting structural evolution. Meanwhile, the connection type of Li n polyhedra experiences transitions from vertex-or edge sharing, to face sharing, leading to a diverse distribution and connectivity of interstitial electrons. All identified electrides exhibit anionic electrons-dominated metallicity. More interestingly, Li 9 Te, with the highest content of Li 6 octahedra, is superconducting with a critical temperature (T c ) of 10.2 K at 75 GPa, which is much higher than typical electrides (e.g., 12CaO • 7Al 2 O 3 , Ca 2 N, and Y 2 C). Its superconductivity mainly originates from the coupling between hybridized electrons (anionic and atomic non-s-state ones) and Te-dominated phonons.

Predicted superconductivity and superionic state in the electride Li5N under high pressure

“…The superconducting critical temperature of Li 5 N decreases with increasing pressure, in contrast to the response of the other electride superconductor Li 6 C [10]. According to the phonon dispersion curve [46] and the Eliashberg spectral function [47] shown in figure 3(a), phonons below 10 THz at 150 GPa contribute 58.5% to the EPC constant, indicating that the low-frequency phonon modes (especially at the Z point) determine the T c of Li 5 N. In addition, the PHDOS (figure 1(d)) shows a tendency for phonons to migrate from low to high frequencies, resulting in fewer phonons in the low-frequency state, which may account for the weakened λ (table 2). Since the DFT calculations are based on 0 K temperature, which is far from the actual environment, it is necessary to consider the effect of different temperatures on the Li 5 N structure.…”

Coexistence of superconductivity and electride states in Ca2H with an antifluorite-type motif under compression

“…For example, 0D electrides Pnnm Y 3 Xe 34 and P 6 3 / mmc Y 3 Si 35 were reported to have computed T c values of 10.8 K at 75 GPa and 14.5 K at 50 GPa, respectively. For Li-containing electrides, 36–39 C 2/ c Li 6 P with dumbbell-like interstitial electrons that play a crucial role in promoting superconductivity has a notable predicted T c of 39.3 K at 270 GPa. 40 Furthermore, the ESCs formed by lithium and group-IV elements exhibit more fascinating properties including Cmcm -I Li 5 C 41 ( T c = 5.7 K at 95 GPa) with one-dimensional (1D) zigzag-like interstitial electrons, Li 6 C 42 ( T c = 10 K at 80 GPa) having unusual sp-hybridized cage-state interstitial quasiatoms (ISQs), and Li 5 Si 43 ( T c = 1.1 K at 0 GPa) having two-dimensional (2D) Kagome anionic electronic states.…”

“…For example, 0D electrides Pnnm Y 3 Xe 34 and P6 3 /mmc Y 3 Si 35 were reported to have computed T c values of 10.8 K at 75 GPa and 14.5 K at 50 GPa, respectively. For Li-containing electrides, [36][37][38][39] C2/c Li 6 P with dumbbell-like interstitial electrons that play a crucial role in promoting superconductivity has a notable predicted T c of 39.3 K at 270 GPa. 40 Meanwhile, both electride behavior 47 and superconductivity with a calculated T c of 3 K at 31 GPa 48 and observed T c of 2 K at 48 GPa 49 were unveiled in the simple cubic phase of calcium.…”

Superconducting Li11Sb2 electride at ambient pressure

“…Our predicted Li 6 P ( T c = 39.3 K) 6 and designed Li 8 Au ( T c = 73.1–81.2 K) 22 have refreshed the electride superconductivity records twice in a row. Besides, a large amount of superconducting Li-rich electrides have been theoretically proposed such as CaLi 2 , 23 Li 8 Cs, 24 Li 5 C, 7,25 Li 5 S, 26 Li 9 Te, 27 Li 10 Se, 28 Li 3 Ar, 29 and Li 5 He 2 . 30 Unfortunately, these pressure-induced electrides are rarely quenched to ambient pressure resulting from the poor adaptability of atoms and IAEs to the unbalanced force caused by pressure change.…”