Strong magnetic instability in correlated metallic Bi₂Ir₂O₇

Abstract

We report an experimental/theoretical study of single-crystal Bi(2)Ir(2)O(7) that possesses a metallic state with strongly exchange-enhanced paramagnetism. The ground state of Bi(2)Ir(2)O(7) is characterized by the following features: (1) a divergent low-temperature magnetic susceptibility that indicates no long-range order down to 50 mK; (2) strongly field-dependent coefficients of the low-temperature T and T(3) terms of the specific heat; (3) a conspicuously large Wilson ratio R(W) ≈ 53.5; and (4) unusual temperature and field dependences of the Hall resistivity that abruptly change below 80 K, without any clear correlation with the magnetic behavior. All these unconventional properties suggest the existence of an exotic ground state in Bi(2)Ir(2)O(7).

Infrared study of the electronic structure of the metallic pyrochlore iridate Bi2Ir2O7

“…From this common aspect of (semi)metallic iridates, Peak α in Bi 2 Ir 2 O 7 might be assigned as the correlation-induced interband transition. However, at the moment the correlated metallic state in Bi 2 Ir 2 O 7 is not reproduced in the theoretical calculations [22,23]. We note that even the previous LDA+U calculation with U ≤ 2 eV did not address the correlation-induced band splitting in metallic pyrochlore iridates [23].…”

“…In the semimetal phase where the charge gap is closed but the coherent peak is absent, the optical conductivity is predicted to increase as the frequency increases from 0 = ω . Therefore, the spectral form of our far-IR conductivity data may suggest that the Weyl semimetal phase could be relevant for [23], which might be also relevant to the non-trivial topological phase.…”

“…Due to the crystal-field splitting in the IrO 6 octahedron, the Ir 5d bands are divided into two bands, t 2g and e g bands. The strong spin-orbit coupling further splits the t 2g bands into fourfold-degenerate J eff,3/2 and doubly-degenerate J eff,1/2 [4,14,22,23].…”

“…We discuss the relevance of our findings to the hypothesis of non-trivial topological states [13][14][15][16]. were combined in a 50 ml Pt crucible in a molar ratio of 40:60 [23]. The reagents were placed in 50 ml…”

“…There is no evidence of the material being sensitive to air. The synchrotron x-ray refinement revealed that our samples are of a single phase, and the crystalline structure is a cubic with the space group m Fd 3 [23]. Information on the structural properties is provided in the Appendix.…”