Honda Z, Katsumata K, Kikkawa A, Yamada K
Faculty of Engineering, Saitama University, Urawa, Saitama 338-8570, Japan.
Phys Rev Lett. 2005 Aug 19;95(8):087204. doi: 10.1103/PhysRevLett.95.087204.
Magnetic susceptibility and heat capacity measurements as a function of temperature on a single-crystal sample of a spin-ladder material, Na2Co2(C2O4)3(H2O)2, are reported. Principal susceptibilities, parallel and perpendicular to the ladder direction, respectively, show broad maxima around 22 and 17 K. Both susceptibilities decay exponentially down to about 5 K and thereafter they are essentially independent of temperature. These findings amount to a signature of a quantum phase transition from a spin-liquid to Néel ordered state previously predicted theoretically. No anomaly is found in the heat capacity around the transition temperature.
报道了对自旋梯子材料Na2Co2(C2O4)3(H2O)2单晶样品的磁化率和热容量随温度变化的测量结果。分别平行和垂直于梯子方向的主要磁化率在22K和17K左右显示出宽峰。两种磁化率均呈指数衰减至约5K，此后它们基本上与温度无关。这些发现构成了从理论上先前预测的自旋液体到奈尔有序态的量子相变的特征。在转变温度附近的热容量中未发现异常。
