Pair density wave at high magnetic fields in cuprates with charge and spin orders

Abstract

In underdoped cuprates, the interplay of the pseudogap, superconductivity, and charge and spin ordering can give rise to exotic quantum states, including the pair density wave (PDW), in which the superconducting (SC) order parameter is oscillatory in space. However, the evidence for a PDW state remains inconclusive and its broader relevance to cuprate physics is an open question. To test the interlayer frustration, the crucial component of the PDW picture, we perform transport measurements on charge-and spin-stripe-ordered La 1.7 Eu 0.2 Sr 0.1 CuO 4 and La 1.48 Nd 0.4 Sr 0.12 CuO 4 in perpendicular magnetic fields (H ⊥), and also with an additional field applied parallel to CuO 2 layers (H ∥). We detect several phenomena predicted to arise from the existence of a PDW, including an enhancement of interlayer SC phase coherence with increasing H ∥. These data also provide much-needed transport signatures of the PDW in the regime where superconductivity is destroyed by quantum phase fluctuations.

Magnetic field reveals vanishing Hall response in the normal state of stripe-ordered cuprates

“… a , b Regions of T and H with different signs of R H for La 1.7 Eu 0.2 Sr 0.1 CuO 4 and La 1.48 Nd 0.4 Sr 0.12 CuO 4 , respectively. c , d Comparison of the results for R H to the other transport data 3 , 4 for La 1.7 Eu 0.2 Sr 0.1 CuO 4 and La 1.48 Nd 0.4 Sr 0.12 CuO 4 , respectively. T c ( H ) (black squares): boundary of the vortex solid in which ( T < T c ) = 0 and R H = 0, as expected for a superconductor.…”

“…strong superconducting (SC) phase fluctuations, persists in two-dimensional (2D) CuO 2 layers, all the way up to the upper critical field H c2 . It is in this regime that recent electrical transport measurements have also revealed 4 the signatures of a spatially modulated SC state referred to as a pair density wave 5 (PDW). The normal state, found at H > H c2 , is highly anomalous 3 : it is characterized by a weak, insulating T -dependence of the in-plane longitudinal resistivity, , without any sign of saturation down to at least , and the negative magnetoresistance (MR).…”

“…However, the Hall behavior in the T → 0, H > H c2 regime has remained mostly unexplored. In particular, recent studies of the La 2− x − y Sr x (Nd,Eu) y CuO 4 compounds have demonstrated 3 , 4 that reliable extrapolations to the T → 0 normal state can be made only by tracking the evolution of SC correlations down to and [T/K] ≫ 1, but there have been no studies of the Hall effect in stripe-ordered cuprates that extend to that regime of T and H and, specifically, to the anomalous normal state at H > H c2 .…”

“…Therefore, we measure the Hall effect on La 1.7 Eu 0.2 Sr 0.1 CuO 4 and La 1.48 Nd 0.4 Sr 0.12 CuO 4 (see Methods) over the entire in-plane T - H vortex phase diagram previously established 3 , 4 for T down to and fields up to T/K, and deep into the normal state. Combining the results of several techniques allows us to achieve an unambiguous interpretation of the Hall data for H < H c2 , and reveal novel properties of the normal state for H > H c2 .…”

“…T c ( H ) (black squares): boundary of the vortex solid in which ( T < T c ) = 0 and R H = 0, as expected for a superconductor. The upper critical field H c2 ( T ) ~ H peak ( T ); H peak ( T ) (dark green dots) are the fields above which the magnetoresistance changes from positive to negative 3 , 4 . The low- T , viscous vortex liquid (VL) regime (light violet) is bounded by T c ( H ) and, approximately, by T peak ( H ) (positions of the peak in ( T ); open blue diamonds), H * ( T ) (crossover between non-Ohmic and Ohmic behavior 3 ; open royal squares), or H peak ( T ); here the behavior is metallic ( d / d T >0) with ( T → 0) = 0 and R H = 0.…”