Controlling the carrier concentration of the high temperature superconductor Bi2Sr2CaCu2O{8+x} in Angle Resolved Photoemission Spectroscopy (ARPES) experiments

TL;DR

This study demonstrates how vacuum conditions and temperature can be used to control the carrier concentration of Bi2Sr2CaCu2O8+x in ARPES experiments, enabling in-situ tuning of doping levels for high-temperature superconductor research.

Contribution

The paper introduces a method to modulate the surface carrier concentration of Bi2212 in UHV conditions by adjusting temperature, facilitating in-situ doping control during ARPES measurements.

Findings

Carrier concentration remains stable at low temperatures in high vacuum.

Elevated temperatures cause oxygen loss and decrease carrier concentration.

Method allows in-situ doping control across the phase diagram.

Abstract

We study the variation of the electronic properties at the surface of a high temperature superconductor as a function of vacuum conditions in angle resolved photoemission spectroscopy (ARPES) experiments. Normally, under less than ideal vacuum conditions the carrier concentration of Bi2Sr2CaCu2O{8+x} (Bi2212) increases with time due to the absorption of oxygen from CO2 and CO molecules that are prime contaminants present in ultra high vacuum (UHV) systems. We find that in a high quality vacuum environment at low temperatures, the surface of Bi2212 is quite stable (the carrier concentration remains constant), however at elevated temperatures the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. These two effects can be used to control the carrier concentration in-situ. Our finding opens the possibility of studying the electronic properties of the cuprates as a function of doping across the phase diagram on the same piece of sample (i.e. with the same impurities and defects). We envision that this method could be utilized in other surface sensitive techniques such as scanning tunneling microscopy/spectroscopy.