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arXiv 2302.07543cond-mat.mes-hallcond-mat.str-el
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激子绝缘体的电击穿

Electrical Breakdown of Excitonic Insulator

Yuelin Shao, Xi Dai

AI总结:

本文提出 BCS 极限下激子绝缘体的“多体击穿”机制,通过有限电场 BCS 型试探波函数数值揭示尺寸依赖的两类击穿行为及 I-V“关-开”判据。

摘要:

在本文中,我们针对 BCS 极限下的激子绝缘体提出了一种新的电击穿机制,它与在传统能带绝缘体中观察到的 Zener 击穿机制存在根本差异。我们的新机制源于激子凝聚的多体基态不稳定性,这种不稳定性由电场存在时极化能与凝聚能之间的强烈竞争所导致。我们将该机制称为“多体击穿”。为研究这一新机制,我们提出了一种有限电场下的 BCS 型试探波函数,并用其对多体击穿进行数值研究。结果揭示了两种不同类型的电击穿行为。若系统尺寸大于临界值,施加电场时 Zener 隧穿过程首先开启,但激子能隙仍然存在,直到场强达到多体击穿的临界值;此后激子能隙消失,系统转变为高导电性的金属态。然而,若系统尺寸远小于临界值,由于多体击穿发生在 Zener 隧穿开始之前,中间隧穿相消失。局域能隙的突然消失会在电流-电压(I-V)曲线上产生“关-开”特征,从而提供一种直接区分激子绝缘体与普通绝缘体的方法。

英文摘要:

In this paper, we propose a new electrical breakdown mechanism for exciton insulators in the BCS limit, which differs fundamentally from the Zener breakdown mechanism observed in traditional band insulators. Our new mechanism results from the instability of the many-body ground state for exciton condensation, caused by the strong competition between the polarization and condensation energies in the presence of an electric field. We refer to this mechanism as ``many-body breakdown''. To investigate this new mechanism, we propose a BCS-type trial wave function under finite electric fields and use it to study the many-body breakdown numerically. Our results reveal two different types of electric breakdown behavior. If the system size is larger than a critical value, the Zener tunneling process is first turned on when an electrical field is applied, but the excitonic gap remains until the field strength reaches the critical value of the many-body breakdown, after which the excitonic gap disappears and the system becomes a highly conductive metallic state. However, if the system size is much smaller than the critical value, the intermediate tunneling phase disappears since the many-body breakdown happens before the onset of Zener tunneling. The sudden disappearance of the local gap leads to an ``off-on'' feature in the current-voltage ($I-V$) curve, providing a straightforward way to distinguish excitonic insulators from normal insulators.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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