Indications of an Electronic Phase Transition in Two-Dimensional SuperconductingYBa2Cu3O7−xThin Films Induced by Electrostatic Doping

In operando evidence of deoxygenation in ionic liquid gating of YBa 2 Cu 3 O 7-X

“…We also want to point out that our results are consistent with those of previous studies on IL gating of YBCO samples, where reversible and hysteretic behavior were observed (16,18), and also with the structural changes after IL gating recently reported in VO 2 films (33) (suggesting deoxygenation) and in cuprates (34) (suggesting oxygen displacement rather than deoxygenation), although we go one step further in demonstrating in operando deoxygenation during the gating process by a spectroscopic tool sensitive to oxygen bonding. We note that other electrochemical processes like protonation and hydrogenation have been previously reported for electrolyte-gated VO 2 thin films (35,36).…”

“…Specifically, in the case of high-temperature cuprate superconductors (16)(17)(18)(19)(20), a striking similarity between the bulk phase diagram and the one achieved with the EDL technique was observed. This result demonstrated that the application of positive gate voltages to hole-doped cuprate EDL transistors induces the depletion of charge carriers.…”

“…Gating experiments allowing its controlled modification have attracted much attention (2)(3)(4)(5)(6)(7)(8), and in recent years, unprecedented changes in the carrier concentration of complex materials have been achieved by using electric double-layer (EDL) techniques that use ionic liquids (ILs) as gate dielectrics (9)(10)(11). Superconductivity has been induced in otherwise band-insulating materials such as SrTiO 3 (STO) (12), ZrNCl (13), KTaO 3 (14), or MoS 2 (15), and the superconducting properties of several cuprates have been tuned to the insulating state (16)(17)(18)(19)(20). These results have focused much attention on the EDL technique not only from an applied point of view but also for providing an opportunity to obtain fundamental knowledge about the phase diagrams.…”

Ionic liquid gating of ultra-thin YBa2Cu3O7−x films

“…31 Focusing on the latter, it is apparent that while it displays a similar T c than the measurements shown for comparison, its normal state resistivity is increased (similarly to Ref. 8), and its critical current is reduced by %40%.…”

“…More recently, due to the large charge accumulation (Dn 2D % 10 14 À 10 15 cm À2 ) realized using electrical double layer (EDL) transistor structures, 2,3 there was a renew of interest in field effect doping of HTSCs and several cuprates; among them, YBa 2 Cu 3 O 7Àx (YBCO) quite rapidly showed a strong tuning of T c . [4][5][6][7][8] In this work, we carefully study the evolution of T c and of the critical current density (J c ) during an EDL-field effect experiment in the underdoped state of YBCO using an ionic liquid (IL). By comparing our low-temperature data with the literature on underdoped films and bulks, we show that upon a negative bias increase in V g , the transport properties of the device stay coherent with the commonly observed self-field transport properties of doped YBCO.…”