Tuning theJeff=12insulating state via electron doping and pressure in the double-layered iridate Sr3Ir

L Li

¹

,

P. P. Kong

²

,

Tongfei Qi

³

et al.

Abstract

Sr 3 Ir 2 O 7 exhibits a novel J eff =1/2 insulating state that features a splitting between J eff =1/2 and 3/2 bands due to spin-orbit interaction. We report a metal-insulator transition in Sr 3 Ir 2 O 7 via either dilute electron doping (La 3+ for Sr 2+ ) or application of high pressure up to 35 GPa. Our study of single-crystal Sr 3 Ir 2 O 7 and (Sr 1-x La x ) 3 Ir 2 O 7 reveals that application of high hydrostatic pressure P leads to a drastic reduction in the electrical resistivity by as much as six orders of magnitude at a critical pressure, P C = 13.2 GPa, manifesting a closing of the gap; but further increasing P up to 35 GPa produces no fully metallic state at low temperatures, possibly as a consequence of localization due to a narrow distribution of bonding angles θ. In contrast, slight doping of La 3+ ions for Sr 2+ ions in Sr 3 Ir 2 O 7 readily induces a robust metallic state in the resistivity at low temperatures; the magnetic ordering temperature is significantly suppressed but remains finite for (Sr 0.95 La 0.05 ) 3 Ir 2 O 7 where the metallic state occurs. The results are discussed along with comparisons drawn with Sr 2 IrO 4 , a prototype of the J eff = 1/2 insulator.

Evolution of magnetism in single-crystalCa2Ru1−xIrxYuan1, Terzic2, Wang3 et al. 2015Phys. Rev. BSelf Cite493751View full textAdd to dashboardCite

“…Since Ir doping further reduces Θ, it is not surprising that T N2 steadily rises with x, as shown in The heat capacity C(T ) data for 0.016 ≤x≤ 0.65 show weak or no anomaly at T N and T N2 , while the anomaly around T MI for x = 0.016 confirms that the metal-insulator transition involves a structural phase transition between the high-T tetragonal to low-T orthorhombic distortion [12,13], as shown in Fig.5a. Interestingly, the heat capacity of Sr 2 IrO 4 also shows no corresponding anomaly at the magnetic ordering temperature 240 K, which one of its signature features of the J eff =1/2 insulator [32].…”

“…One profound result of this competition is that 5d-iridates exhibit complex magnetic states with high critical temperatures, such as Sr 2 IrO 4 (T N = 240 K) [22], Sr 3 Ir 2 O 7 (T N = 285 K) [31,32] and BaIrO 3 (T C = 183 K) [33,34]. It is established that the magnetic moment and ordering temperature are closely associated with the Ir-O-Ir bond angle Θ [35].…”

Evidence for ordered magnetic moments at oxygen sites in antiferromagneticSr2IrO4andSr3Ir2

“…While the situation is not as clear for Sr 3 Ir 2 O 7 , earlier reports in the literature have reported the observation of a rapid decease in magnetization at T D ≃ 50 K and reversal in the basal plane below 20 K under field-cooled conditions at 0.01 T. This has only been observed at low magnetic induction (below ∼ 0.2 T). 10,15 Again, these anomalies exhibit a certain correlation with the charge sector as inferred from the sharp increase in the electrical resistivity. 10,14,15 In contrast to these two cases, no clear anomaly suggesting a phase transition has been observed in the bulk properties of orthorhombic SrIrO 3 (n = ∞) over the temperature range from ambient to the liquid helium temperature.…”

“…14, 15 The anomaly has also been shown to be closely linked with the charge sector; the dielectric response exhibits crossover from relaxor-like to ferroelectric behavior as the temperature is decreased past T M . These features correlate with the reduction in the Ir-O-Ir bond angle, which suggests a change in spin canting induced by alteration of the exchange coupling.…”

First-Order Melting of a Weak Spin-Orbit Mott Insulator into a Correlated Metal

“…Consistent with the idea of a delicate Mott state, Sr-327 has recently been shown to manifest metallic behavior under small levels of La substitution (electron doping) [13]. However, little remains understood regarding the nature of the metallic state realized upon carrier substitution and the means through which the parent J eff ¼ 1=2 Mott state collapses.…”