Tomonaga-Luttinger liquid in a quasi-one-dimensional = 1 antiferromagnet observed by specific heat measurements

比熱測定による=1の準一次元反強磁性鎖における朝永・ラッティンジャー流体的振る舞い

萩原 政幸*; 辻井 宏之*; Rotundu, C. R.*; Andraka, B.*; 高野 安正*; 立岩 尚之   ; 小林 達生*; 鈴木 隆史*; 菅 誠一郎*

Hagiwara, Masayuki*; Tsujii, Hiroyuki*; Rotundu, C. R.*; Andraka, B.*; Takano, Yasumasa*; Tateiwa, Naoyuki; Kobayashi, Tatsuo*; Suzuki, Takafumi*; Suga, Seiichiro*

準一次元系磁性物質Ni(CHN)(NO)(ClO)(NTENP)の磁場中比熱測定を行った。スピン鎖に並行に磁場を加えると、臨界磁場以上でスピンギャップが消滅し、磁気秩序転移温度より高温では比熱が温度に依存する振る舞いを示すことが明らかとなった。本研究から明らかとなった、朝永-ラッティンジャー流体的振る舞いについて理論モデルを用いて解析する。

Specific-heat experiments on single crystals of the = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(CHN)(NO)(ClO) (NTENP) have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat () is proportional to temperature () above a critical field , at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio = increases as the magnetic field approaches from above. The data are in good quantitative agreement with the prediction of the =1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing conclusive evidence for a Tomonaga-Luttinger liquid.