Imbalanced Fermi systems and exotic superconducting phases

TL;DR

This paper explores the emergence of the exotic FFLO superconducting phase in imbalanced fermionic systems, highlighting its coexistence with magnetism and its significance in understanding complex quantum phases.

Contribution

It discusses the conditions and properties of the FFLO phase in Pauli limited superconductors under population imbalance, revealing its unconventional coexistence with magnetism.

Findings

FFLO phase characterized by spatially modulated superconductivity.

Coexistence of superconductivity and magnetism in FFLO.

Implications for understanding exotic quantum phases.

Abstract

Quantum many body phases, in competition or coexistence has always been a fascinating area of research in condensed matter physics. One of the most widely investigated scenario of phase competition is that between superconductivity and magnetism, which in spite of several decades of research continues to bring up new surprises till date. While superconductivity and magnetism are naively considered to be antagonists, there are several circumstances where these many body phases can be found to be cooperating, coexisting and even promoting each other. The results of such cooperative behavior are found to show up as exotic quantum phases. In this chapter we discuss about such an exotic superconducting phase, which comes to life when a particular class of superconducting material viz. "Pauli limited superconductors" are subjected to an imbalance between the population of the fermionic species undergoing pairing. The consequence of such an imbalance is the emergence of a non-trivial spatially modulated superconducting phase, popularly known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. Characterized by a finite momentum pairing between the fermionic species the FFLO phase hosts a non zero magnetization, leading to an unconventional coexistent phase of superconductivity and magnetism.