Insight on the electronic state of Sr₂IrO₄revealed by cationic substitutions

Abstract

We report the electrical resistivity, thermoelectric power and magnetization of Sr2−xLaxIrO4 (x = 0 and 0.05) and Sr2Ir1−yRhyO4 (y = 0.05, 0.1 and 0.2) measured below room temperature. In Sr2IrO4, electrons (La substitution) or holes (Rh substitution) can be doped, which lead to a strong decrease of the resistivity. In particular, a nearly-metallic state is realized in the case of Rh doping. The thermoelectric power turns out to be metallic-like for y = 0.2. The presence of a gap in the electronic band structure is robust against these substitutions. From various experimental data, similarities with the 3D charge density wave compound, BaBiO3, are suggested. Nevertheless, rather than a charge density wave, our scenario implies the presence of a spin density wave.

Tuning electronic structure via epitaxial strain in Sr2IrO4 thin films

“…However, the temperature-dependent data for bulk crystal shows that 6 the optical peak energies decrease as temperature increases, which is an opposite behavior to our observations in thin films, in which optical peak energies increase under tensile strain. Whereas the thermal effect should increase the overall lattice parameters of a sample, our thin films under biaxial in-plane tensile-strain expand only the in-plane lattice parameters, but reduce the out-ofplane lattice parameters.…”

“…To understand the physics of Sr 2 IrO 4 and to find a way of tuning its multiple, competing interactions, experimental studies of chemical doping [3][4][5][6][7][8][9] and high pressure 10 have been recently conducted. However, chemical doping often has multiple consequences, such as changes in crystal structure and the valence states of the transition metal element, which can make it difficult to achieve a desired state.…”

Electron and hole doping in the relativistic Mott insulator Sr2IrO4 : A first-principles study using band unfolding technique

“…It was proposed that Ir→Rh chemical substitution leads to hole-transfer from Rh to Ir ideally leading to the formation of Ir 5+ and Rh 3+ ions [17,21,22]. While formally correct, this picture is rather simplified as it does not consider possible changes in the Ir-d/O-p hybridization and does not account for the presence of the two inequivalent Ir I and Ir II sites in the compound (see Fig.…”

“…Among the different forms of electron and hole doping tested in this system, the most studied ones are the substitution of Sr 2+ with La 3+ (electron doping) and the homovalent heterosubstitution of 5d 5 Ir 4+ with 4d 5 Rh 4+ (effective hole doping) [15,[17][18][19][20][21][22][23][24][25][26]. In one of the first studies, Lee and coworkers conducted a systematic investigation of La, Rh, and Ru doping in Sr 2 IrO 4 by means of optical spectroscopy and found that the J eff = 1/2 state remains spectroscopically robust upon doping and that in all cases doping induces an insulator-to-metal transition (IMT) for moderately low dopant concentrations (≈ 5%) [19].…”

Dilute magnetism and spin-orbital percolation effects inSr2Ir1−xRhxClancy1, Lupascu2, Gretarsson3 et al. 2014Phys. Rev. B9591270View full textAdd to dashboardCite

“…The structural and magnetic similarities between these compounds have led to natural associations with superconductivity, and recent theoretical proposals 7,8 have spurred renewed interest in the properties of doped Sr 2 IrO 4 . Although many forms of electron, hole, and isoelectronic doping have been experimentally tested to date [9][10][11][12][13][14][15][16][17][18][19][20] , there is still much to learn about the impact of doping on the spin-orbital Mott insulating ground state. Sr 2 Ir 1−x Rh x O 4 represents an ideal candidate for experimental doping studies.…”