# Nematic Fluctuations in the Cuprate Superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$

## TL;DR

This study uses electronic Raman scattering to detect nematic fluctuations in a cuprate superconductor, suggesting a link to a van Hove singularity rather than a conventional quantum critical point, shedding light on high-temperature superconductivity.

## Contribution

It provides the first evidence of nematic fluctuations near the pseudogap endpoint in Bi2212, indicating a non-canonical origin related to band structure features.

## Key findings

- Enhanced nematic fluctuations near pseudogap endpoint
- Deviation from canonical quantum critical behavior
- Link between nematic instability and van Hove singularity

## Abstract

Establishing the presence and the nature of a quantum critical point in their phase diagram is a central enigma of the high-temperature superconducting cuprates. It could explain their pseudogap and strange metal phases, and ultimately their high superconducting temperatures. Yet, while solid evidences exist in several unconventional superconductors of ubiquitous critical fluctuations associated to a quantum critical point, in the cuprates they remain undetected until now. Here using symmetry-resolved electronic Raman scattering in the cuprate Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, we report the observation of enhanced electronic nematic fluctuations near the endpoint of the pseudogap phase. While our data hint at the possible presence of an incipient nematic quantum critical point, the doping dependence of the nematic fluctuations deviates significantly from a canonical quantum critical scenario. The observed nematic instability rather appears to be tied to the presence of a van Hove singularity in the band structure.