Quantum-Critical Spin Dynamics in Quasi-One-Dimensional Antiferromagnets

Abstract

By means of nuclear spin-lattice relaxation rate T(1)(-1), we follow the spin dynamics as a function of the applied magnetic field in two gapped quasi-one-dimensional quantum antiferromagnets: the anisotropic spin-chain system NiCl(2)-4SC(NH(2))(2) and the spin-ladder system (C(5)H(12)N)(2)CuBr(4). In both systems, spin excitations are confirmed to evolve from magnons in the gapped state to spinons in the gapless Tomonaga-Luttinger-liquid state. In between, T(1)(-1) exhibits a pronounced, continuous variation, which is shown to scale in accordance with quantum criticality. We extract the critical exponent for T(1)(-1), compare it to the theory, and show that this behavior is identical in both studied systems, thus demonstrating the universality of quantum-critical behavior.

Nuclear Magnetic Resonance Reveals Disordered Level-Crossing Physics in the Bose-Glass Regime of the Br-Doped Ni(Cl1−xBrxOrlova1, Blinder2, Kermarrec3 et al. 2017Phys. Rev. Lett.152390View full textAdd to dashboardCite

“…The system is thus in the 1D Tomonaga-Luttinger liquid regime above the BEC phase [11]. Below H c2 one thus observes high T…”

“…Between the two critical magnetic fields H c1 and H c2 , it presents a magnetic-field-induced low-temperature (T ) 3D-ordered phase, described as a Bose-Einstein condensate (BEC) [2][3][4][5]. DTN is particularly convenient for studying this phase; for a magnetic field (H) applied along the chain c axis, its (body-centered) tetragonal symmetry [6] ensures the required axial symmetry of the spin Hamiltonian with respect to H. The values of its exchange couplings and D (J c /k B = 2.2 K, J a,b /k B = 0.18 K, D/k B = 8.9 K) [7,8] make the BEC phase easily accessible, with H c2 = 12.32 T [9][10][11] and the phase transition temperature T c below T cmax = 1.2 K. The system can be reasonably considered as quasi-one-dimensional (1D), with J a,b /J c = 0.08.…”

EffectiveS=12description of theS=1chain with strong easy-plane anisotropy

“…Detailed analysis of spin contribution to the total thermal conductivity is a nontrivial task due to the pres- ence of phononic contribution. Also, the DTN compound is a quasi-1D material with J ⊥ /J ≃ 0.18, and for temperatures below T N < 1.2 K (T /J 0.5) is in a 3D ordered state [6,8,11,40] with long-range correlations [41,40].…”

Phonon-Modulated Magnetic Interactions and Spin Tomonaga-Luttinger Liquid in thep-Orbital AntiferromagnetCsO2

“…Pq, 75.30.Et, 75.25.Dk, In many magnetic insulators, spins are well decoupled from other degrees of freedom, which implies simple Hamiltonians completely defined by the short-range magnetic exchange interactions. Model systems of this kind provide an excellent playground for the understanding of collective quantum phenomena, including TomonagaLuttinger liquid (TLL) in one-dimensional (1D) antiferromagnets [1], Bose-Einstein condensation of magnons in dimer spin systems [2], quantum criticality in gapped antiferromagnets [3][4][5][6] and spin-liquid behavior in frustrated spin systems [7].In molecular solids, a class of magnetic insulators containing molecules as structural and magnetic units, spins cannot be decoupled from lattice and orbital degrees of freedom. This is particularly pronounced in systems based on small and light anionic O − 2 molecules: alkali superoxides, AO 2 (A = Na, K, Rb, Cs) [8][9][10][11], and alkali sesquioxides, A 4 O 6 (A = Rb, Cs) [12][13][14][15].…”