Periodic Density of States Modulations in Superconducting $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$

TL;DR

This study uses scanning tunneling spectroscopy to reveal static stripe-like modulations in the electronic density of nearly optimally doped Bi-2212, linking these features to the superconducting gap and suggesting a shared microscopic origin.

Contribution

First observation of static stripe-like density modulations in Bi-2212 using STS, showing their relation to the superconducting gap and potential broken symmetry.

Findings

Stripe modulations strongest at half the superconducting gap energy

Modulations aligned with Cu-O bonds with four lattice constant periodicity

Density of states shifts from above to below the gap, indicating a common origin

Abstract

In this paper we show, using scanning tunneling spectroscopy (STS), the existence of static striped density of electronic states in nearly optimally doped $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$ in zero field. The observed modulation is strongest at roughly half the superconducting gap energy and is aligned with the Cu-O bonds, with a periodicity of four lattice constants, exhibiting features characteristic of a two-dimensional system of line objects. These features also exhibit asymmetries between the two orthogonal directions locally, pointing to a possible broken symmetry state (i. e., stripe phase). We further show that the density of states modulation manifests itself as a shift of states from above to below the superconducting gap. The fact that a single energy scale (i. e., the gap) appears for both superconductivity and stripes suggests that these two effects have the same microscopic origin.