Superconductivity in quasi-one-dimensional Cs2Cr3As3 with large interchain distance

Abstract

Since the discovery of high-temperature superconductivity (SC) in quasi-two-dimensional copper oxides, a few layered compounds, which bear similarities to the cuprates, have also been found to host the unconventional SC. Our recent observation of SC at 6.1 K in correlated electron material K2Cr3As3 represents an obviously different paradigm, primarily because of its quasi-one-dimensional ( The revolutionary discovery of high-temperature SC in cuprates in the 1980s [1] has inspired the unprecedented enthusiasm to explore new superconductors, especially in transition-metal compounds. The continuous efforts over a quarter century have led to the discoveries of unconventional SC in a few classes of materials including iron pnictides [2], which bear two fundamental similarities to the cuprates -strong electron correlations and quasi two dimensionality. It is of great interest to explore possible unconventional SC in a Q1D material with significant electron correlations.Our recent observation of SC at T c = 6.1 K in K 2 Cr 3 As 3 realized the above possibility [3]. Unconventional SC was preliminarily evidenced by the peculiar properties including linear temperature dependence of resistivity in the normal state and extremely high upper critical field exceeding the Pauli limit by a factor of four [3] [7][8][9][10][11] in the normal state is evidenced by the NQR measurements [6]. So far, all the investigations [3-6] consistently point to the unconventional SC in the Q1D Crbased material.It is known that Peierls transition easily occurs in Q1D metallic systems [11,12], which prevents the appearance of SC [13]. The interchain coupling serves as a crucial control parameter, thus it is of interest to explore other possible analogues with varying interchain coupling strength. By the replacement of K + with Rb +

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

“…Unexpectedly, for this 133-type RbCr 3 As 3 , the onset superconducting T c is enhanced up to 7.3 K, which is much higher than that of the 233-type Rb 2 …”

Observation of a Raman-active phonon with Fano line shape in the quasi-one-dimensional superconductorK2Cr3As3

“…Interestingly, a recent theoretical study indicates that the next-neighbor Cr-Cr exchange interaction is by far the strongest in this system [10], and the modulation of the Cr-Cr intra-layer distance should thus lead to the strongest magneto-elastic effect. The importance of the intra-layer Cr-Cr distance is also supported by the sensitivity of superconductivity to isovalent substitution of K with larger Cs [3] or Rb [4] atoms, and to applying hydrostatic or uniaxial pressure [24]. Even though our results do not allow us to comment directly on the unconventional nature of superconductivity in K 2 Cr 3 As 3 , they certainly suggest that the magnetic fluctuations reported in this system are coupled to the electronic structure via lattice vibrations, which may be of crucial importance in elaborating models for superconductivity in this material.…”

“…1. By taking into account the peak symmetries and their proximity in energy with the calculated values, we tentatively assign E (1) , E (2) and E (3) to phonons No. 6, No.…”

“…When the electron-phonon coupling is strong enough, the spectral lineshape of Raman phonon excitations is characterized by an asymmetric profile called Fano lineshape [1]. Despite a superconducting transition temperature (T c ) up to 6.1 K comparable to that of conventional superconductors, the recently discovered quasi-one-dimensional superconductors A 2 Cr 3 As 3 (A = K, Rb, Cs) have exotic properties that tentatively earned them the label of unconventional superconductors [2][3][4], such as an abnormal power law divergence of the 75 As nuclear spin lattice relaxation rate near T c [5]. Penetration depth measurements suggest a nodal line in the superconducting gap [6] and a large zero temperature upper critical field H c2 (0) compared to the Pauli limit has been attributed to a spin triplet p-wave pairing [2], in agreement with a theoretical study revealing strong ferromagnetic fluctuations caused by the frustration of Cr moments within one layer [7].…”

Temperature and angular dependence of the upper critical field in K2Cr3As3

“…Recently, SC was discovered in a Cr-based family A 2 Cr 3 As 3 (A = K [11], Rb [12] and Cs [13]). The new materials possess a quasi-one-dimensional (quasi-1D) crystal structure characterized by infinite [(Cr 3 As 3 )…”