Enhancement of the Thermal Conductivity in gaped Quantum Spin Chains

Vicente Álvarez, Claudius Gros

Shintaro Takayoshi, Thierry Giamarchi

David L. Huber

Keiji Saito, Seiji Miyashita

We study mechanism of magnetic energy transport, motivated by recent measurements of the thermal conductivity in low dimensional quantum magnets. We point out a possible mechanism of enhancement of the thermal conductivity in gapped magnetic system, where the magnetic energy transport plays a crucial role. This mechanism gives an interpretation for the recent experiment of CuGeO_3, where the thermal conductivity depends on the crystal direction.

Carlos Mejía-Monasterio, Hannu Christian Wichterich

Mitsuhide Sato, Takayuki Kawamata, Naoki Sugawara +5 more

In order to clarify the origin of the enhancement of the thermal conductivity in the Bose-Einstein Condensed (BEC) state of field-induced triplons, we have measured the thermal conductivity along the [101] direction parallel to spin-chains, κ ||[101] , and perpendicular to spin-chains, κ ⊥[101] , of the S =1/2 bond-alternating spin-chain system Pb 2 V 3 O 9 in magnetic fields up to 14 T. With increasing field at 3 K, it has been found that both κ ||[101] and κ ⊥[101] are suppressed in the gapped normal state in low fields. In the BEC state of field-induced triplons in high fields, on the other hand, κ ||[101] is enhanced with increasing field, while κ ⊥[101] is suppressed. That is, the thermal conductivity along the direction, where the magnetic interaction is strong, is markedly enhanced in the BEC state. Accordingly, our results suggest that the enhancement of κ ||[101] in the BEC state is caused by the enhancement of the thermal conductivity due to triplons on the basis of the two-fluid model, as in the case of the superfluid state of liquid 4 He.