Université Paris-Saclay

报告摘要：

Phase transitions are fundamental phenomena in condensed matter physics accompanied by a spontaneous symmetry breaking at a critical point. In the framework of Landau theory [1], these transitions occur when an order parameter changes discontinuously (first-order transition) or continuously (second-order transition) as external conditions, such as temperature or magnetic field, are varied. Structural phase transitions, for instance, involve a lattice symmetry breaking and are typically first order, while second-order transitions, such as superconductivity breaks the unitary gauge symmetry. These thermodynamic phase transitions are driven by thermal fluctuations at finite temperature.

In contrast, quantum phase transitions occur at absolute zero temperature, driven not by thermal but by quantum fluctuations [2]. These transitions happen at a quantum critical point (QCP), where the system undergoes a fundamental change in its ground state as a function of a non-thermal control parameter, such as pressure, doping, or magnetic field. Near the QCP, exotic phenomena such as non-Fermi liquid behavior [3][4], strange metallicity [5][6] and unconventional superconductivity [4][7] often emerge, making the study of quantum criticality central to understanding strongly correlated systems.

Traditionally, phase transitions are explored by varying thermodynamic parameters like temperature or magnetic field. In this presentation, I will expose an alternative approach: driving symmetry breaking through uniaxial pressure. I will describe our efforts to adapt uniaxial pressure environments to several experimental probes such as transport, infrared spectroscopy and ARPES. Uniaxial pressure allows precise control of structural distortions, directly tuning crystallographic symmetries. This environment enables a deeper investigation into the interplay between structure and electronic properties, particularly in systems where strong electron-phonon interactions mediate phase transitions and lead to the emergence of exotic electronic states.

[1] L. Landau, Zh. Eksp. Teor. Fiz. 7, 19-32 (1937).

[2] H. v. Löhneysen, Rev. of Mod. Phys. 79, 1015 (2007).

[3] P. Coleman, Phys. B: Cond. Matt. 259-261, 353-358 (1999).

[4] T. Shibauchi et al., Ann. Rev. Cond. Matt. Phys. 5, 113-135 (2014).

[5] B. Keimer et al., Nature 518, 179-186 (2015).

[6] B. Michon et al., Nat. Comm. 14, 3033 (2023).

[7] J.G. Bednorz and K.A. Müller, Z. Phys. B Cond. Matt. 64, 189-193 (1986).

报告人简介：

Dr. Bastien Michon earned his PhD through a joint program between the University of Grenoble-Alpes (France) and the University of Sherbrooke (Canada). He has built a strong academic and international background in experimental condensed matter physics, with expertise in transport measurements, specific heat, and infrared spectroscopy under extreme conditions – including high magnetic fields (up to 35 T) and ultra-low temperatures (down to 50 mK) – to investigate quantum materials such as unconventional superconductors and Weyl semimetals. His recent research has focused on quantum criticality in high-Tc cuprate superconductors, leading to first-author publications in high-impact journals such as Nature, Nature Communications, and Physical Review X.

Following his appointment as Assistant Professor at the City University of Hong Kong, he secured over 6 million RMB in research funding from multiple sources, including the NSFC and the Research Grants Council of Hong Kong.

He recently completed a postdoctoral fellowship at the Laboratoire de Physique des Solides (LPS), Université Paris-Saclay, where he adapted uniaxial pressure environments for a range of experimental techniques – transport, infrared spectroscopy and ARPES – in collaboration with LPS, SOLEIL Synchrotron and international partners, to study the strontium ruthenate family, notably the superconducting monolayer Sr₂RuO₄ and the metamagnetic bilayer Sr₃Ru₂O₇. He is now transitioning to a new postdoctoral position at SOLEIL Synchrotron starting in October 2025, where he will further expand this work and integrate it into new experimental platforms – including Scanning Near-field Optical Microscopy (SNOM).

邀 请 人：吴泉生 特聘研究员

联 系 人：王慧颖 why@iphy.ac.cn

报告地点：怀柔园区MA楼505会议室

腾讯会议：107-397-496

会议密码：2025

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