Charge density wave fluctuations in La2-xSrxCuO4 and their competition with superconductivity (1404.7474v3)

Abstract: We report hard (14 keV) x-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La2-xSrxCuO4. All samples show charge-density-wave (CDW) order with onset temperatures in the range 51-80 K and ordering wavevectors close to (0.23,0,0.5). The CDW is strongest with the longest in-plane correlation length near 1/8 doping. On entering the superconducting state the CDW is suppressed, demonstrating the strong competition between the charge order and superconductivity. CDW order coexists with incommensurate magnetic order and wavevectors of the two modulations have the simple relationship $\delta_{charge}= 2\delta_{spin}$. The intensity of the CDW Bragg peak tracks the intensity of the low-energy (quasi-elastic) spin fluctuations. We present a phase diagram of La2-xSrxCuO4 including the pseudogap phase, CDW and magnetic order.

Charge Density Wave Fluctuations in La$_{2-x}$Sr$_{x}$CuO$_{4}$ and Their Competition with Superconductivity

The research presented in this paper investigates the charge density wave (CDW) order within the La$_{2-x}$Sr$_{x}$CuO$_{4}$ high-temperature superconductor system across three doping compositions ($x=0.11,0.12,0.13$). Utilizing hard x-ray diffraction, the authors provide detailed insights into CDW fluctuations and their impact on the superconductivity. Their findings contribute significantly to the understanding of the electronic phase landscape in cuprate superconductors.

Charge density wave order is identified as a pervasive feature in underdoped high-temperature superconductors, which has been substantiated by various experimental techniques in previous studies on different cuprate families. In La$_{2-x}$Sr$_{x}$CuO$_{4}$, a CDW order is detected with onset temperatures between 51 K and 80 K, and characterized by ordering wavevectors near the values of (0.23,0,0.5). Notably, this order is most pronounced at a doping level near 1/8, where both the intensity and correlation length of the CDW reach their peak values, signifying the strongest competition with superconductivity.

One remarkable aspect of this research is the observed suppression of CDW order upon transitioning to the superconducting state. This suppression illustrates the dynamic interplay and competition between the CDW and superconducting phases. Moreover, it signifies the intertwined nature of different order parameters and suggests the necessity to understand the multifaceted interrelations within the cuprate systems.

A phase diagram illustrating the relationship between CDW order, pseudogap phase, spin density wave (SDW) order, and superconductivity is constructed based on experimental data and prior research. This diagram emphasizes that the pseudogap phase transition precedes CDW order, with the latter developing within the pseudogap region. The correlation wavevectors demonstrate a simple connection where $$\boldsymbol{\delta}_{\mathrm{charge}}= 2\boldsymbol{\delta}_{\mathrm{spin}}$$, highlighting a close relationship between charge and spin correlations.

The implications of these findings are profound. The suppression of CDW order when superconductivity manifests may imply potential pathways to modify the superconductive properties by managing CDW states. The competition observed could be indicative of fundamental constraints or opportunities to influence superconductivity, particularly at specific doping levels.

Future research could explore the theoretical models that explain the interplay between these orders—focusing, for instance, on how fluctuations in order parameters might be engineered or controlled to enhance superconductivity. Similarly, further refinement of the phase diagram is warranted to understand more accurately the nature of interactions between CDW, SDW, and superconducting states across different doping levels.

In conclusion, this paper delivers compelling evidence on the competitive and cooperative phenomena within La$_{2-x}$Sr$_{x}$CuO$_{4}$. As the field progresses, such insights provide a foundation for unraveling the intricate mechanisms underpinning high-temperature superconductivity in cuprates and perhaps aid in the quest to design materials with improved superconducting properties.