Jeong M, Schmidiger D, Mayaffre H, Klanjšek M, Berthier C, Knafo W, Ballon G, Vignolle B, Krämer S, Zheludev A, Horvatić M
Laboratoire National des Champs Magnétique Intenses, LNCMI-CNRS (UPR3228), UGA, UPS, and INSA, Boîte Postale 166, 38042, Grenoble Cedex 9, France.
Laboratory for Quantum Magnetism, Institute of Physics, Ecole Polytechnique Féderale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2016 Sep 2;117(10):106402. doi: 10.1103/PhysRevLett.117.106402. Epub 2016 Sep 1.
We present a direct NMR method to determine whether the interactions in a Tomonaga-Luttinger liquid (TLL) state of a spin-1/2 Heisenberg antiferromagnetic ladder are attractive or repulsive. For the strong-leg spin ladder compound (C_{7}H_{10}N){2}CuBr{4} we find that the isothermal magnetic field dependence of the NMR relaxation rate T_{1}^{-1}(H) displays a concave curve between the two critical fields bounding the TLL regime. This is in sharp contrast to the convex curve previously reported for a strong-rung ladder, (C_{5}H_{12}N){2}CuBr{4}. We show that the concavity and the convexity of T_{1}^{-1}(H), which is a fingerprint of spin fluctuations, directly reflect the attractive and repulsive fermionic interactions in the TLL, respectively. The interaction sign is alternatively determined from an indirect method combining bulk magnetization and specific heat data.
我们提出了一种直接核磁共振（NMR）方法，用于确定自旋1/2海森堡反铁磁梯子的汤川-卢廷格液体（TLL）态中的相互作用是吸引性的还是排斥性的。对于强腿自旋梯子化合物（C₇H₁₀N）₂CuBr₄，我们发现NMR弛豫率T₁⁻¹（H）的等温磁场依赖性在界定TLL区域的两个临界场之间呈现出一条凹曲线。这与先前报道的强梯级梯子（C₅H₁₂N）₂CuBr₄的凸曲线形成鲜明对比。我们表明，T₁⁻¹（H）的凹性和凸性作为自旋涨落的一个特征，分别直接反映了TLL中吸引性和排斥性的费米子相互作用。相互作用的符号也可以通过结合体磁化强度和比热数据的间接方法来确定。
