Dichotomy between attractive and repulsive Tomonaga-Luttinger liquids in spin ladders

Minki Jeong, D. Schmidiger, H. Mayaffre, M. Klanjšek, C. Berthier, W. Knafo, G. Ballon, B. Vignolle, S. Krämer, A. Zheludev, M. Horvatić

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16 Citations (Scopus)


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  (C7H10N)2CuBrwe find that the isothermal magnetic field dependence of the NMR relaxation rate  T1−1 (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,  (C5H12N)2CuBr4. We show that the concavity and the convexity of T1−1 (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.
Original languageEnglish
Article number106402
Number of pages6
JournalPhysical Review Letters
Issue number10
Publication statusPublished - 1 Sept 2016


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