The phonon thermal Hall angle in black phosphorus.

The origin of phonon thermal Hall Effect (THE) observed in a variety of insulators is yet to be identified. Here, we report on the observation of a thermal Hall conductivity in a non-magnetic elemental insulator, with an amplitude exceeding what has been previously observed. In black phosphorus (BP), the longitudinal (κ), and the transverse, κ, thermal conductivities peak at the same temperature and at this peak temperature, the κ/κ/B is ≈ 10-10 T.

Phonon thermal Hall effect in a metallic spin ice.

It has become common knowledge that phonons can generate thermal Hall effect in a wide variety of materials, although the underlying mechanism is still controversial. We study longitudinal κ and transverse κ thermal conductivity in PrIrO, which is a metallic analog of spin ice. Despite the presence of mobile charge carriers, we find that both κ and κ are dominated by phonons.

Phonon hydrodynamics and ultrahigh-room-temperature thermal conductivity in thin graphite.

Allotropes of carbon, such as diamond and graphene, are among the best conductors of heat. We monitored the evolution of thermal conductivity in thin graphite as a function of temperature and thickness and found an intimate link between high conductivity, thickness, and phonon hydrodynamics. The room-temperature in-plane thermal conductivity of 8.

Observation of Poiseuille flow of phonons in black phosphorus.

The travel of heat in insulators is commonly pictured as a flow of phonons scattered along their individual trajectory. In rare circumstances, momentum-conserving collision events dominate, and thermal transport becomes hydrodynamic. One of these cases, dubbed the Poiseuille flow of phonons, can occur in a temperature window just below the peak temperature of thermal conductivity.

Colossal Seebeck Coefficient of Hopping Electrons in (TMTSF)_{2} PF_{6}.

We report on a study of the Seebeck coefficient and resistivity in the quasi-one-dimensional conductor (TMTSF)_{2} PF_{6} extended deep into the spin-density-wave state. The metal-insulator transition at T_{SDW}=12  K leads to a reduction in carrier concentration by 7 orders of magnitude. Below 1 K, charge transport displays the behavior known as variable range hopping.

Low-dimensional structure and magnetism of the quantum antiferromagnet Rb4Cu(MoO4)3 and the structure of Rb4Zn(MoO4)3.

Single crystals of the quantum low-dimensional antiferromagnet Rb(4)Cu(MoO(4))(3) and the nonmagnetic analogue Ru(4)Zn(MoO(4))(3) have been synthesized by a flux-growth method. Detailed structural studies indicate that the Cu(II)-O network separated by a MoO(4) layer has a strongly anisotropic hybridization along the a-axis, forming a quasi-one-dimensional (1-d) chain of Cu(II) S = 1/2 spins. Furthermore, our low-temperature thermodynamic measurements have revealed that a quantum paramagnetic state with Wilson ratio approximately 2 remains stable down to at least 0.

Time-reversal symmetry breaking and spontaneous Hall effect without magnetic dipole order.

Spin liquids are magnetically frustrated systems, in which spins are prevented from ordering or freezing, owing to quantum or thermal fluctuations among degenerate states induced by the frustration. Chiral spin liquids are a hypothetical class of spin liquids in which the time-reversal symmetry is macroscopically broken in the absence of an applied magnetic field or any magnetic dipole long-range order. Even though such chiral spin-liquid states were proposed more than two decades ago, an experimental realization and observation of such states has remained a challenge.