Two-step condensation of the charged Bose gas

TL;DR

This paper investigates the phase transitions of a charged Bose gas in magnetic fields, revealing a two-step condensation process and effective one-dimensional behavior at low temperatures.

Contribution

It extends the conventional model to include excited kinetic states in the lowest Landau level, highlighting their role in large magnetic field regimes.

Findings

Identification of two diffuse phase transitions in specific heat

System behaves as a one-dimensional free boson system below the cyclotron frequency

Gradual condensation occurs at low temperatures

Abstract

The condensation of the spinless ideal charged Bose gas in the presence of a magnetic field is revisited. The conventional approach is extended to include the macroscopic occupation of excited kinetic states lying in the lowest Landau level, which plays an essential role in the case of large magnetic fields. In that limit, signatures of two diffuse phase transitions (crossovers) appear in the specific heat. In particular, at temperatures lower than the cyclotron frequency, the system behaves as an effectively one-dimensional free boson system, with the specific heat equal to $(1/2)N k_B T$ and a gradual condensation at lower temperatures.