Anomalous magnetoresistance due to longitudinal spin fluctuations in a Jeff\u2009=\u20091/2 Mott semiconductor

Lin Hao,Cristian D Batista,Junyi Yang,Daniel Haskel,Kipton Barros,Jian Liu,Jong-Woo Kim,Zhentao Wang,M P M Dean,Joshua Sanchez,Yongseong Choi,D Meyers,Gilberto Fabbris,Philip J Ryan,Jiun-Haw Chu

doi:10.1038/s41467-019-13271-6

Abstract

As a hallmark of electronic correlation, spin-charge interplay underlies many emergent phenomena in doped Mott insulators, such as high-temperature superconductivity, whereas the half-filled parent state is usually electronically frozen with an antiferromagnetic order that resists external control. We report on the observation of a positive magnetoresistance that probes the staggered susceptibility of a pseudospin-half square-lattice Mott insulator built as an artificial SrIrO3/SrTiO3 superlattice. Its size is particularly large in the high-temperature insulating paramagnetic phase near the Néel transition. This magnetoresistance originates from a collective charge response to the large longitudinal spin fluctuations under a linear coupling between the external magnetic field and the staggered magnetization enabled by strong spin-orbit interaction. Our results demonstrate a magnetic control of the binding energy of the fluctuating particle-hole pairs in the Slater-Mott crossover regime analogous to the Bardeen-Cooper-Schrieffer-to-Bose-Einstein condensation crossover of ultracold-superfluids.

Highlights

As a hallmark of electronic correlation, spin-charge interplay underlies many emergent phenomena in doped Mott insulators, such as high-temperature superconductivity, whereas the half-filled parent state is usually electronically frozen with an antiferromagnetic order that resists external control
The Slater–Mott crossover regime is the particle–hole counterpart of the famous Bardeen–Cooper–Schrieffer (BCS)-to-Bose–Einstein condensation (BEC) crossover observed in ultracold-superfluids[19,20,21]
We report an experiment-theory-combined investigation on the spin and charge interlay in a square-lattice iridate built as an artificial superlattice (SL) of SrIrO3 and SrTiO3, which is well described by a two-dimensional (2D) single-band Hubbard model in the crossover regime between the Mott[3] and the Slater[21] limits

Summary

Introduction

As a hallmark of electronic correlation, spin-charge interplay underlies many emergent phenomena in doped Mott insulators, such as high-temperature superconductivity, whereas the half-filled parent state is usually electronically frozen with an antiferromagnetic order that resists external control. While a huge variety of unusual symmetry-breaking orderings can emerge as the ground state of correlated electrons, the disordered state above the phase transition is often even more enigmatic due to fluctuations that are challenging for experimental characterization and theoretical description[1] This is true when strong interplay between the spin and charge degrees of freedom is in play, such as the fascinating normal state of high-temperature superconductors[2]. The significantly reduced Coulomb interaction and larger extension of the 5d orbitals shift these materials toward the Slater regime corresponding to the weakcoupling limit Both of these two perturbative approaches predict antiferromagnetic insulating ground state, but neither of them provides a complete description of the experimentally observed behaviors[14].

Methods

Results

Conclusion