Cs133andAs75NMR investigation of the normal metallic state of quasi-one-dimensional

Abstract

We report 133 Cs NMR and 75 As Nuclear Quadrupole Resonance (NQR) measurements on the normal metallic state above Tc of a quasi-one-dimensional superconductor Cs2Cr3As3 (Tc < 1.6 K). From the 133 Cs NMR Knight shift 133 K measured at the Cs1 site, we show that the uniform spin susceptibility χspin increases from 295 K to ∼ 60 K, followed by a mild suppression; χspin then levels off below ∼10 K. In contrast, a vanishingly small magnitude of 133 K indicates that Cs2 sites contribute very little to electrical conduction and the exchange interactions between 3d electrons at Cr sites. Low frequency Cr spin dynamics, reflected on 75 As 1/T1T (the nuclear spin-lattice relaxation rate 1/T1 divided by temperature T ), shows an analogous trend as χspin. Comparison with the results of 1/T1T near Tc with K2Cr3As3 (Tc = 6.1 K) and Rb2Cr3As3 (Tc = 4.8 K) establishes a systematic trend that substitution of K + ions with larger alkali ions progressively suppresses Cr spin fluctuations together with Tc.

Superconductivity in the regime of attractive interactions in the Tomonaga-Luttinger liquid

“…1a) in the structure, where only one of them (most probably Rb1 at the 3k position) strongly couples to the Mo 3 As 3 chains. We note that the analogous two-component NMR spectrum has been observed also in 133 Cs NMR of Cs 2 Cr 3 As 3 [24].…”

“…Molybdenum-chalcogenide (Li x MoS 2 , Na 2−δ Mo 6 Se 6 ) and molybdenum-oxide (Li 0.9 Mo 6 O 17 ) nanotubes/chains [17][18][19][20] display many unusual properties associated with TLLs, but at the same time they also show a high degree of disorder due to the intercalation of metallic atoms between the nanotubes, which mask the TLL and superconducting properties. The disorder effects seem to be less important in Cr-pnictide quasione-dimensional metals, e.g., A 2 Cr 3 As 3 (A=K, Rb, Cs) with Cr 3 As 3 chains as main building units, which remarkably also show low-temperature superconductivity with the critical temperature T c ≈ 5 K [21][22][23][24][25][26][27][28][29]. There seems to be a growing consensus for the unconventional singlet superconducting states in this family of materials based on the large specific-heat jump at T c and large upper critical fields exceeding Pauli limit [21,30], absence of the Hebel-Slichter coherence peak and the power-law dependence of nuclear spin-lattice relaxation rates [24,28] and the penetration depth proportional to temperature [25] that implies the nodal-type of a superconducting gap.…”

“…The disorder effects seem to be less important in Cr-pnictide quasione-dimensional metals, e.g., A 2 Cr 3 As 3 (A=K, Rb, Cs) with Cr 3 As 3 chains as main building units, which remarkably also show low-temperature superconductivity with the critical temperature T c ≈ 5 K [21][22][23][24][25][26][27][28][29]. There seems to be a growing consensus for the unconventional singlet superconducting states in this family of materials based on the large specific-heat jump at T c and large upper critical fields exceeding Pauli limit [21,30], absence of the Hebel-Slichter coherence peak and the power-law dependence of nuclear spin-lattice relaxation rates [24,28] and the penetration depth proportional to temperature [25] that implies the nodal-type of a superconducting gap. Moreover, a possible ferromagnetic quantum critical point has been proposed based on the tuning of the nuclear spin-lattice relaxation rates by the Cr-As-Cr angle [31].…”

“…Moreover, a possible ferromagnetic quantum critical point has been proposed based on the tuning of the nuclear spin-lattice relaxation rates by the Cr-As-Cr angle [31]. However, the complicated electronic structure comprising two quasi-one-dimensional (1D) and one threedimensional (3D) Fermi surface [32] and the presence of a Korringa component in the nuclear spin-lattice relaxation cast some doubts on the direct applicability of the TLL model for A 2 Cr 3 As 3 [24].…”

Superconductivity at 7.3 K in the 133-type Cr-based RbCr 3 As 3 single crystals

“…More interestingly, many experimental and theoretical research results point to intriguing spin-triplet paring superconductivity in these A 2 Cr 3 As 3 superconductors [4,[12][13][14][15][16][17]. Nevertheless, these A 2 Cr 3 As 3 compounds are extremely reactive when exposed in air and easily oxidized during most experimental procedures, which hinders many further studies for its intrinsic physical characteristics.…”