史哲雨

2019-present                                            研究员

华东师范大学精密光谱科学与技术国家重点实验室

2016-2019                                             Research Fellow

School of Physics and Astronomy, Monash University

I am a theoretical physicist at the State Key Laboratory of Precision Spectroscopy, ECNU. I had my Ph.D training in the field of cold atom physics, however, I am also intrigued by various subjects related to quantum matter, such as condensed matter physics, quantum optics and etc.

Below are selected works of mine along with brief comments.

1. Ce Wang, Chang Liu, Zhe-Yu Shi

Complex Contact Interaction for Systems with Short-Range Two-Body Losses, Physical Review Letters 129, 203401 (2022).

In this work, we consider quantum gases with two-particle losses. We find that in the zero-range loss limit, the open system dynamics is governed by a single complex parameter, i.e. the complex s-wave scattering length, which is a natural extension of the real s-wave scattering length in the closed system. We also provide the correct renormalization and regularization methods for zero-range loss models and utilize these models for the investigation of Bose gases with weak interaction and two-particle losses.

2. Zhe-Yu Shi, Chao Gao, Hui Zhai

Ideal-Gas Approach to Hydrodynamics, Physical Review X 11, 041031 (2021).

This work is inspired by an intriguing experiment (Physical Review X 9, 021035) conducted by Prof. J. Dalibard’s group at Paris University. In the experiment, it is discovered that for a two-dimensional strongly interacting (in the sense that the system is in the Thomas-Fermi region) Bose gas, the dynamics shows an entirely surprising and unexpected periodic behavior in a harmonic trap if the initial state is prepared as the ground state in an equilaterial triangle trap. We solve the puzzle and reveal the underlying mechanism of this periodic behavior by showing that the hydrodynamics of this system may be, surprisingly, mapped to the non-interacting dynamics of an ideal gas. Interestingly, the momentum distribution of the corresponding ideal gas system possesses a very peculiar geometric property that suggests the hydrodynamics of this Bose system has a certain Fermionic nature.

3. Chao Gao, Hui Zhai, Zhe-Yu Shi

Dynamical fractal in quantum gases with discrete scaling symmetry, Physical Review Letters 122, 230402 (2019).

In this work we discover an unexpected relation between the Weierstrass function and a quantum system with discrete scaling symmetry. The Weierstrass function is a remarkable function discovered by Karl Weierstrass in 1872 (Mathematische werke: Abhandlungen II, Vol. 2, pp. 71–74.). It is the first instance of a real function that is continuous everywhere but differentiable nowhere. It is also arguably the first example of a self-similar fractal curve, despite that the term "fractal" was not coined until almost a century after its discovery. Inspired by the resemblance of its self-similarity and the self-similarity of eigenstates states in a quantum system with discrete scaling symmetry(e.g. the Efimov states in a three-body system), we find that there is a hidden connection between these two worlds. Use a concrete example that can be realized in a one-dimensional ultracold atomic gas, we demonstrate that the Loschmidt amplitude of a quantum system with discrete scaling symmetry is indeed a fractal Weierstrass function.

4. Shujin Deng, Zhe-Yu Shi, Pengpeng Diao, Qianli Yu, Hui Zhai, Ran Qi, Haibin Wu

Observation of the Efimovian expansion in scale-invariant Fermi gases, Science 353, 371-374 (2016).

This work is donw in collaboration with the cold atom experiment group led by Prof. Haibin Wu at ECNU. In this work, we generalize the celebrated Efimov physics to the time domain and observe the so-called Efimovian expansion in unitary Fermi gas. In the conventional Efimov physics, the continuous scaling symmetry in real space plays an important role. Interestingly, my colleagues and I find that it is also possible to extend this continuous scaling symmetry to the time domain by considering a time varying harmonic trap. If this continuous symmetry further breaks into a discrete one, similar to the scenario occurs in the conventional Efimov system, the system dynamics would exhibit log-periodic behavior such that the size of the atomic cloud displays a series of steps in geometric progressions during the expansion process.

欢迎对理论物理感兴趣的同学（包括本科生，研究生）加入课题组。

联系方式：zyshi@lps.ecnu.edu.cn

超冷原子气体等量子物质的理论研究。
主要包括：

1. 量子气体中的少体问题，包括Efimov物理，弯曲空间中的少体问题等。

2. 强相互作用的量子气体，包括强相互作用的费米和玻色气体中的多体与少体物理。

3. 超冷原子气体中远离平衡的动力学，包括Efimovian膨胀，动力学分形等新奇的动力学行为。

4. 转角二维或三维晶格体系中的新奇物理。

5. 开放系统物理，包括开放超冷原子气体及激子-极化激元体系中的非厄米物理。