Zeeman and Orbital Limiting Fields: Separated Spin and Charge Degrees of Freedom in Cuprate Superconductors

TL;DR

This paper explains the differing limiting magnetic fields observed in cuprate superconductors by showing they correspond to the same pseudogap energy scale when considering separated spin and charge degrees of freedom, unifying experimental findings.

Contribution

It introduces a framework connecting Zeeman and orbital limiting fields to the pseudogap energy scale, highlighting separated spin and charge degrees of freedom in cuprates.

Findings

Zeeman and orbital fields converge to the pseudogap energy scale $T^*$.

Separated spin and charge degrees of freedom exist in different Fermi surface regions.

Reconciliation of disparate experimental results in high-Tc cuprates.

Abstract

Recent in-plane thermal (Nernst) and interlayer (tunnelling) transport experiments in Bi$_2$Sr$_2$CaCu$_2$O$_{8+y}$ high temperature superconductors report hugely different limiting magnetic fields. Based on pairing (and the uncertainty principle) combined with the definitions of the Zeeman energy and the magnetic length, we show that in the underdoped regime both fields convert to the same (normal state) pseudogap energy scale $T^*$ upon transformation as orbital and spin (Zeeman) critical fields, respectively. We reconcile these seemingly disparate findings invoking separated spin and charge degrees of freedom residing in different regions of a truncated Fermi surface.