Giant isotropic magneto-thermal conductivity of metallic spin liquid candidate Pr2Ir2O7 with quantum criticality

Abstract

Spin liquids are exotic states with no spontaneous symmetry breaking down to zero-temperature because of the highly entangled and fluctuating spins in frustrated systems. Exotic excitations like magnetic monopoles, visons, and photons may emerge from quantum spin ice states, a special kind of spin liquids in pyrochlore lattices. These materials usually are insulators, with an exception of the pyrochlore iridate Pr2Ir2O7, which was proposed as a metallic spin liquid located at a zero-field quantum critical point. Here we report the ultralow-temperature thermal conductivity measurements on Pr2Ir2O7. The Wiedemann–Franz law is verified at high fields and inferred at zero field, suggesting no breakdown of Landau quasiparticles at the quantum critical point, and the absence of mobile fermionic excitations. This result puts strong constraints on the description of the quantum criticality in Pr2Ir2O7. Unexpectedly, although the specific heats are anisotropic with respect to magnetic field directions, the thermal conductivities display the giant but isotropic response. This indicates that quadrupolar interactions and quantum fluctuations are important, which will help determine the true ground state of this material.

Three-dimensional sandglass magnet with non-Kramers ions

“…However, promising three-dimensional (3D) QSL candidates are still rare since higher dimensionality suppresses the quantum fluctuations. Hyperkagome Na 4 Ir 3 O 8 [25][26][27] and pyrochlore Pr 2 Ir 2 O 7 [28][29][30][31] are the only two representative 3D QSL candidates and have been the subject of extensive studies. Even if the absence of magnetic order and spin dynamics are found, it is not sufficient to claim a QSL material, since those observations can be explained by other mechanisms.…”

Phonon spectrum of Pr$_2$Zr$_2$O$_7$ and Pr$_2$Ir$_2$O$_7$ as an evidence of coupling of the lattice with electronic and magnetic degrees of freedom

“…This material is suggested to be a Luttinger semimetal, that is to host a quadratic band touching at the Γ point of the Brillouin zone (BZ) [6]. Early on it was suggested to be a chiral metallic spin liquid [5,[7][8][9]. We found that a comparative study of their phonon spectra can reveal information of the coupling of the lattice to magnetic and electronic degrees of freedom which is difficult to identify otherwise.…”

Three-dimensional Sandglass Magnet with Non-Kramers ions

“…However, promising three-dimensional (3D) QSL candidates are still rare since higher dimensionality suppresses the quantum fluctuations. Hyperkagome Na 4 Ir 3 O 8 [25][26][27] and pyrochlore Pr 2 Ir 2 O 7 [28][29][30][31] are two representative 3D QSL candidates and have been the subject of extensive studies.…”