Violation of the Spin Statistics Theorem and the Bose-Einstein Condensation of Particles with Half Integer Spin

TL;DR

This paper explores the unconventional Bose-Einstein condensation of spin-1/2 particles under magnetic fields, revealing unique excitation spectra and the violation of superfluidity criteria, challenging traditional spin-statistics relationships.

Contribution

It demonstrates that spin-1/2 particles can form a Bose condensate with distinct excitations, contradicting the conventional spin-statistics theorem and providing new insights into quantum critical states.

Findings

Identification of two massive Higgs excitations.

Discovery of two Goldstone modes with different spectra.

Bose condensate does not support superfluidity, violating Landau criterion.

Abstract

We consider the Bose condensation of particles with spin 1/2. The condensation is driven by an external magnetic field. Our work is motivated by ideas of quantum critical deconfinement and bosonic spinons in spin liquid states. We show that both the nature of the novel Bose condensate and the excitation spectrum are fundamentally different from that in the usual integer spin case. We predict two massive ("Higgs") excitations and two massless Goldstone excitations. One of the Goldstone excitations has a linear excitation spectrum and another has quadratic spectrum. This implies that the Bose condensate does not support superfluidity, the Landau criterion is essentially violated. We formulate a "smoking gun" criterion for searches of the novel Bose condensation.