Speaker: Vivek Thampy, Brookhaven National Laboratory
Program Description
Charges doped into the copper oxide planes of the insulating parent compounds frequently organize into rich electronic textures. The most well-known example is the charge-spin stripe state, first seen in La1.48Nd0.4Sr0.12CuO4 and, subsequently, in a number of other “214” cuprates, most notably La2−xBaxCuO4(LBCO). More recently, charge modulations have also been observed in other cuprate families including YBa2Cu3O6+y (“123”), and (Bi2−xPbx)(Sr2−yLay)Can−1CunO2n+4+δ. This suggests that the charge ordering (CO) in the copper oxide planes stems from a fundamental underlying instability common across the different cuprate families. In my talk, I will first present Cu L3 edge soft x-ray scattering studies comparing the lattice modulation associated with the charge modulation in YBa2Cu3O6.6 with that associated with the well-known charge and spin stripe order in La1.875Ba0.125CuO4, and show that despite significant distinctions, the amplitudes of the charge modulations in the two systems are comparable in magnitude. I will then report the observation of a unique rotated charge modulation in La1.88Sr0.12CuO4 (LSCO), which we believe provides important clues towards a unified description of charge order in all the different cuprate families. Our results demonstrate that charge order in LSCO is modulated with a wave-vector close to the other “214” compounds that share a common lineage, i.e. La2CuO4. The response of the charge order to superconductivity in LSCO is similar to Yb- and Bi- based cuprates that it shares structural similarities with, i.e. orthorhombicity. The unique rotated nature of the stripes we observe in LSCO provide an important signature of how stripes interact with subtle structural distortions – something that can be used to distinguish rival theories of stripe formation in the cuprates.
