Abstract

A long-range interacting spin chain placed in a staggered magnetic field can exhibit either first order phase transition or second order phase transition depending on the magnetic field intensity. The first order phase transition of this model is known to be accompanied with the temperature jump phenomenon in the microcanonical ensemble, while this anomalous temperature jump phenomenon can not be observed in the canonical ensemble. We obtain the crossover phase transition properties passing from a microcanonical to a canonical ensemble, by placing this previously isolated spin chain model in contact with a two-level system that acts as a thermal reservoir. The magnitude of the temperature jump monotonically decreases with the increase of the size of the thermal reservoir. And the microcanonical phase diagram can gradually turn into the canonical phase diagram by increasing the number of particles of the reservoir.

Graphical abstract

中文翻译：

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从微经典系到经典系：具有长程相互作用的自旋链的相变

摘要

放置在交错磁场中的远距离相互作用的自旋链可根据磁场强度呈现一阶相变或二阶相变。已知该模型的一阶相变伴随着微规范集合中的温度跃变现象，而这种异常温度跃变现象在规范集合中无法观察到。通过将先前隔离的自旋链模型与充当热库的两级系统接触，可以获得从微规范到规范集合的交叉相变特性。温度跃变的幅度随储热库大小的增加而单调减小。

图形概要