Pr2Ir2O7 : When Luttinger Semimetal Meets Melko-Hertog-Gingras Spin Ice State

Abstract

We study the band structure topology and engineering from the interplay between local moments and itinerant electrons in the context of pyrochlore iridates. For the metallic iridate Pr2Ir2O7, the Ir 5d conduction electrons interact with the Pr 4f local moments via the f -d exchange. While the Ir electrons form a Luttinger semimetal, the Pr moments can be tuned into an ordered spin ice with a finite ordering wavevector, dubbed "Melko-Hertog-Gingras" state, by varying Ir and O contents. We point out that the ordered spin ice of the Pr local moments generates an internal magnetic field that reconstructs the band structure of the Luttinger semimetal. Besides the broad existence of Weyl nodes, we predict that the magnetic translation of the "Melko-Hertog-Gingras" state for the Pr moments protects the Dirac band touching at certain time reversal invariant momenta for the Ir conduction electrons. We propose the magnetic fields to control the Pr magnetic structure and thereby indirectly influence the topological and other properties of the Ir electrons. Our prediction may be immediately tested in the ordered Pr2Ir2O7 samples. We expect our work to stimulate a detailed examination of the band structure, magneto-transport, and other properties of Pr2Ir2O7. arXiv:1712.06534v2 [cond-mat.str-el]

Dielectric and electronic properties of three-dimensional Luttinger semimetals with a quadratic band touching

“…The dependence of the RKKY interaction on the helical structure of the eigenstates may help further characterize Luttinger semimetals through their magnetic properties. Moreover, in the case of Pr 2 Ir 2 O 7 , this interaction may be responsible for the magnetic coupling between the Pr local moments [18].…”

“…Such physics is not restricted to linearly dispersing fermions and can also occur at quadratic band touching points [8][9][10][11][12][13]. In three dimensions, the latter can in fact be seen as a parent phase of a Weyl semimetal [14][15][16][17][18]. Materials with strong spin orbit coupling constitute a fruitful platform for the realization of such non-trivial semimetals or metals due to their tendency for band inversion [11].…”

Giant, unconventional anomalous Hall effect in the metallic frustrated magnet candidate, KV 3 Sb 5

“…Metallic materials with frustrated magnetic sublattices, particularly when combined with relativistic carriers, are uncommon, and investigation of their Hall effects has been sparsely performed. For example, the metallic spin liquids, Pr 2 Ir 2 O 7 and LiV 2 O 4 are a Luttinger semimetal and heavyfermion metal, respectively; neither of these has Dirac band crossings or low-mass carriers (29)(30)(31)(32).…”

Electron quasi-itinerancy intertwined with quantum order by disorder in pyrochlore iridate magnetism

“…43,44 Now, the Ir electrons are proposed as Luttinger semimetal, [45][46][47] while the Pr spin is proposed to be proximate to a transition between a U(1) spin liquid and an ordered spin ice. [48][49][50][51] Based on the existing theoretical [15][16][17][46][47][48][52][53][54][55][56][57][58] and experimental works, the true magnetic state of these Irbased pyrochlore systems remains open. In the present paper, we address this problem and provide some understanding.…”