我們研究了二腳(two-leg)的樓梯模型。由先前的研究得知，該模型如果引進了反鐵磁的次近鄰， 則系統擁有兩個相：Haldane 相和單態相(rung-singlet)。但不久前，Starykh 等人提出了，除了前面提 到的兩個相，還有第三個相：二聚化相(columnar dimer)。在我們的研究中，我們計算了二聚化序參量， 發現其序參量在熱力學極限下是不存在的。而且，我們還利用其他間接的數值證明，如分析rung自旋關 聯函數的交點，string關聯函數，和能隙等結果，均發現只有一個相變點的存在，而非兩個。因此，我們 結論在two-leg的樓梯模型？堙A並不存在二聚化相。 In this work, we investigate two-leg spin ladders. As is well known, if the next nearest neighboring couplings are considered, there are two phases existing in this model: Haldane phase and Rung-singlet (RS) phase. However, O. A. Starykh et. al. proposed that there should be another phase, called columnar dimmer (DC) phase, lying between the Haldane phase and the RS phase. We firstly calculated the dimer order parameter to detect the existence of the DC phase. We found that the order parameter disappears in the thermodynamic limit. We also proved the inexistence of the DC phase in other indirect ways. Through careful transition analysis on rung spin correlations, string correlations and the gaps, we inferred that only a phase boundary does exist in the model with the entire parameter range, but not two. Therefore we concluded that the DC phase is not present in the two-leg spin ladder.
