[Paper Review] Hole Superconductivity in MgB_2, Cuprates, and Other Materials

J. E. Hirsch|arXiv (Cornell University)|Jun 18, 2001

Superconductivity in MgB2 and Alloys5 references3 citations

TL;DR

This paper proposes that hole superconductivity—driven by hole undressing rather than electron-phonon coupling—is the universal mechanism underlying superconductivity in MgB₂, cuprates, and conventional superconductors. It presents theoretical evidence for this mechanism and makes specific predictions for MgB₂, unifying diverse superconducting materials under a single framework distinct from BCS theory.

ABSTRACT

The theory of hole superconductivity proposes that MgB_2, and the high Tc cuprates, and the 'conventional superconductors', and all other superconductors, are driven by the same physical mechanism, which is not the electron-phonon interaction. That mechanism, hole undressing, evidence supporting it, and predictions for MgB_2, are briefly reviewed.

Motivation & Objective

• To propose a unified mechanism for superconductivity across diverse materials, including MgB₂ and cuprates.
• To challenge the conventional electron-phonon coupling explanation by introducing hole undressing as the primary driver.
• To provide theoretical evidence and predictions for hole superconductivity in MgB₂.
• To extend the hole superconductivity theory to include conventional superconductors and other materials.
• To unify high-Tc and conventional superconductors under a single theoretical framework.

Proposed method

• The theory of hole superconductivity is applied to analyze MgB₂, cuprates, and conventional superconductors.
• The mechanism relies on the concept of 'hole undressing,' where holes in the system reduce their effective mass and gain coherence.
• The model predicts specific electronic and magnetic responses in MgB₂, such as diamagnetic screening and charge redistribution.
• The theory is contrasted with BCS theory, emphasizing the absence of electron-phonon coupling as the driving force.
• Theoretical predictions are derived from the hole superconductivity framework and compared with experimental observations.
• The approach uses a many-body formalism to describe the collective behavior of holes in the superconducting state.

Experimental results

Research questions

• RQ1 Is hole superconductivity the universal mechanism underlying superconductivity in MgB₂, cuprates, and conventional superconductors?
• RQ2 How does hole undressing differ from electron-phonon coupling in driving superconductivity?
• RQ3 What specific predictions does the hole superconductivity theory make for MgB₂'s electronic and magnetic properties?
• RQ4 Can the same theoretical framework explain both high-Tc cuprates and conventional superconductors?
• RQ5 What evidence supports the hole undressing mechanism over traditional pairing mechanisms?

Key findings

• The paper identifies hole undressing as the fundamental mechanism driving superconductivity in MgB₂, cuprates, and conventional superconductors.
• It argues that electron-phonon coupling is not the primary driver of superconductivity in these materials.
• The theory predicts a specific charge redistribution and diamagnetic screening in MgB₂ consistent with experimental observations.
• The framework unifies high-Tc cuprates and conventional superconductors under a single theoretical mechanism.
• Evidence for hole undressing is presented as central to explaining the superconducting state across different materials.
• The model provides a new explanation for the origin of superconductivity that diverges from the BCS paradigm.