Gain without inversion in quantum systems with broken parities

范德华拓扑铁磁金属碲化锗铁中的破缺反演对称性

Broken inversion symmetry in van der Waals topological ferromagnetic metal iron germanium telluride

本研究利用SHG技术证实碲化锗铁存在反演对称性破缺，揭示其空间群由P63/mmc降至极性P3m1，并阐明Fe空位有序与温度鲁棒性，为其本征自旋轨道转矩和拓扑极性金属态提供结构依据。

Coherent Mechanism of Robust Population Inversion

A coherent mechanism of robust population inversion in atomic and molecular systems by a chirped field is presented. It is demonstrated that a field of sufficiently high chirp rate imposes a certain relative phase between a ground and excited state wavefunction of a two-level system. The value of the relative phase angle is thus restricted to be negative and close to 0 or $-π$ for positive and negative chirp, respectively. This explains the unidirectionality of the population transfer from the ground to the excited state. In a molecular system composed of a ground and excited potential energy …

Invariants of broken discrete symmetries

The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying in particular to acoustic, optical and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.

受迫极化量子系统的自发辐射

Spontaneous emission from driven polar quantum systems

研究揭示受迫极化量子系统中自发辐射机制，通过破除反演对称性改变衰变动力学，展示其在控制自发光中的潜力。

Probing one-dimensional topological phases in waveguide lattices with broken chiral symmetry

One-dimensional lattices with chiral symmetry are known to possess quantized Zak phase and nontrivial topological phases. Here it is shown that quantized Zak phase and nontrivial edge states, partially protected by inversion symmetry rather than chiral symmetry, can be observed and probed in the bulk exploiting continuous-time photonic quantum walk in zig-zag waveguide arrays. Averaged beam displacement measurements can detect quantized Zak phase and non-trivial topological phases in the extended Su-Schrieffer-Heeger model with broken chiral symmetry.

Ultrathin Films of Superconducting Metals as a Platform for Topological Superconductivity

The ingredients normally required to achieve topological superconductivity (TSC) are Cooper pairing, broken inversion symmetry, and broken time-reversal symmetry. We present a theoretical exploration of the possibility of using ultra-thin films of superconducting metals as a platform for TSC. Because they necessarily break inversion symmetry when prepared on a substrate and have intrinsic Cooper pairing, they can be TSCs when time-reversal symmetry is broken by an external magnetic field. Using microscopic density functional theory calculations we show that for ultrathin Pb and $β$-Sn supercon…

Dirac与Schrödinger-Pauli理论中的时间反演对称性

Time inversion symmetry in the Dirac and Schrödinger-Pauli theories

本文指出Schrödinger-Pauli理论在描述破缺时间反演对称性时存在不完备性，揭示了Dirac理论中非相对论电子的内禀Berry曲率及其对反常霍尔电导率的独立贡献。

拓扑绝缘体中表面-体态杂化导致概率密度的反演对称性破缺

Inversion symmetry breaking in the probability density by surface-bulk hybridization in topological insulators

本文用有效连续介质 Hamiltonian 解析研究有限厚拓扑绝缘体薄板，发现表面态与体态杂化可使 Γ 点附近概率密度相对板中心发生自发反演对称性破缺。