Superconductivity in Li-intercalated 1T−SnSe2 driven by electric field gating

Abstract

Creating carrier reservoirs in layered compounds can effectively tune the carrier density, which often induces a variety of emergent properties. Based on solid-ion-conductor gating technique, we successfully induce superconductivity of 4.8 K in ultrathin Li-intercalated SnSe2 samples. The Li + ions are driven in between interspacing of SnSe2 layers and form a single reservoir layer to provide electrons. In addition, a dome-like T c is found through substituting of S for Se, where the optimal T c is 6.2 K for SnSe1.8S0.2. Density functional theory calculations confirm that the intercalated LiSnSe2 is thermodynamically favorable, where the intercalation of Li expands the interlayer spacing by 10% and increases the carrier density by two orders of magnitude. Meanwhile the calculated results reveal that the enhanced electron-phonon interaction due to softened phonon determines the occurrence of superconductivity. Our results demonstrate that this strategy is very effective to explore superconductors in layered materials with narrow bandgap.

Electronic, vibrational, and electron-phonon coupling properties in SnSe$_2$ and SnS$_2$ under pressure

“…The superconducting state is observed to emerge at 18.6 GPa and to reach a maximum T c of about 6.1 K, which remains nearly constant in a large pressure range between 30.1 and 50.3 GPa. Earlier studies have demonstrated superconductivity in bulk and thin films SnSe 2 through intercalation and gating 13,[90][91][92] as well as interface superconductivity in SnSe 2 /ion-liquid and SnSe 2 /graphene 93,94 .…”

Electrochemical Intercalation in Atomically Thin van der Waals Materials for Structural Phase Transition and Device Applications

“…[ 93 ] However, the large radius of F ion impedes its intercalation into 2D materials, given that the intercalation reported may be from the defects in the Basal plane of 2D materials. Subsequently, solid ion conductors containing Li or Na ions are introduced to SIC‐FETs, [ 45–47 ] in which the carrier densities and phase transitions of 2D layered materials can be tuned by driving Li/Na ions in and out of the thin flakes via electrochemical gating. For example, by controlling the Li ion intercalation, a semiconductor–superconductor transition in Li‐intercalated SnSe 2 and a superconducting phase diagram of FeSe have been reported.…”

“…For example, by controlling the Li ion intercalation, a semiconductor–superconductor transition in Li‐intercalated SnSe 2 and a superconducting phase diagram of FeSe have been reported. [ 45–47 ] More importantly, compared with the former approaches, the electrochemical intercalation process is more reversible due to the stability of solid ion conductor and interface between the channels and SIC, rendering it more appropriate for room‐ and low‐temperature transport measurements. It deserves to be noted that besides the transport measurements, in our opinion, the SIC based intercalation approach will take effect in the characterization of intercalation kinetics and stages by in situ tip‐based techniques, such as atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electrochemical microscopy (SECM), and other near field optics, in order to better reveal the structural evolution during the de/intercalation.…”

“…Besides FeSe, other 2D metals and semiconductors present superconducting behavior, which has been enhanced by electrochemical intercalation of ions or molecules. [ 46,77 ] Similarly, based on solid‐ion‐conductor gating technique, Li ions were driven in between interspacing of ultrathin SnSe 2 layers and form a single reservoir layer to provide electrons, leading to the emergence of superconductivity in Li‐intercalated SnSe 2 with T c = 4.8 K. [ 46 ] In addition, through partially substituting S for Se, a domelike T c of 6.2 K for SnSe 1.8 S 0.2 is observed. It has been further demonstrated by DFT calculations that the carrier density of intercalated SnSe 2 compound is enhanced by two orders of magnitude, together with the expanded interlayer spacing by around 10%, and the superconductivity in SnSe 2 is attributed to the enhanced electron–phonon interaction.…”

Photon drag of superconducting fluctuations in 2D systems

“…To date, the transition of TMD and main-group metal dichalcogenide flakes from the normal (resistive) to superconductive phase have been studied in experiments [7][8][9][10][11][12][13][14][15] . However, in the range of temperature close to the phase transition, T T c , the behaviour of TMD flakes in the electromagnetic (EM) field has not been completely studied experimentally, as well as theoretically.…”