Gross violation of the Wiedemann–Franz law in a quasi-one-dimensional conductor

Abstract

When charge carriers are spatially confined to one dimension, conventional Fermi-liquid theory breaks down. In such Tomonaga–Luttinger liquids, quasiparticles are replaced by distinct collective excitations of spin and charge that propagate independently with different velocities. Although evidence for spin–charge separation exists, no bulk low-energy probe has yet been able to distinguish successfully between Tomonaga–Luttinger and Fermi-liquid physics. Here we show experimentally that the ratio of the thermal and electrical Hall conductivities in the metallic phase of quasi-one-dimensional Li0.9Mo6O17 diverges with decreasing temperature, reaching a value five orders of magnitude larger than that found in conventional metals. Both the temperature dependence and magnitude of this ratio are consistent with Tomonaga–Luttinger liquid theory. Such a dramatic manifestation of spin–charge separation in a bulk three-dimensional solid offers a unique opportunity to explore how the fermionic quasiparticle picture recovers, and over what time scale, when coupling to a second or third dimension is restored.

Low‐Cost and Sustainable Organic Thermoelectrics Based on Low‐Dimensional Molecular Metals

“…Similar values of 1.6 W/(m K) in semiconducting, needle-like crystals of functionalized pentacenes have been determined along the stacking direction [27] . The large apparent ph may also point to an increased as predicted and experimentally verified for quasi-onedimensional Luttinger liquids [10,28] . In DCNQI2Cu however, a weaker temperature-dependence of than expected from the WF law is observed.…”

Possible triplet superconductivity in the quasi-one-dimensional conductor Li0.9Mo6O17

“…First of all, we note that at high enough temperatures, the Luttinger liquid effects are observed [44][45][46] in the Li 0.9 Mo 6 O 17 conductor. This naturally reflects the Q1D nature of its electron spectrum (4),(5) and is not crucial for our analysis, since we consider the low temperature region, T < T c = 2.2 K. In this context, it is important that from the theoretical point of view, the FL picture is restored at temperatures lower than t z , t y 10 − 45 K. Another point of concern is the experimentally observed increase of resistivity at T ≤ T min 15 − 30 K. So far, its nature has not been clearly understood.…”

Electrical and thermal transport in the quasiatomic limit of coupled Luttinger liquids

“…For temperatures between the two hopping scales, it would be reasonable to treat the system as a collection of weakly coupled 1D chains as we have done here, and by the nature of the crystal they form an ordered array, again matching our model. Such anisotropic crystals are known to show strong violations of the Wiedemann-Franz law, especially in the Hall direction in a magnetic field 13 . By comparing the measured violations of the Wiedemann-Franz law in these systems with our predictions, it should be possible to estimate the effective Luttinger parameter K for the constituent one-dimensional chains.…”

“…Likewise, the density of states around the Fermi level is predicted to show a distinctive power law behavior 10 ; this was also observed in an artificially created 1D chain 11 . Other observations of Luttinger liquid-like behavior, however, have been made not on actual one-dimensional chains but rather on two-dimensional collections of one-dimensional systems such as in the polymer films that motivated this work 1 or on highly anisotropic three-dimensional crystals [12][13][14] ; it is not immediately clear that the results of these experiments should be directly compared to theories of single Luttinger liquids. Rather, the coupling of 1D chains to form a quasi-2D material may modify or destroy altogether the distinctive signatures of Luttinger liquid behavior.…”