The Laboratoire de Physique des Solides (LPS) is pleased to announce that Antoine Gallo–Frantz has been awarded the 2026 PhD Thesis Prize by the Physics thematic group of the French Crystallographic Association (AFC).
His thesis, entitled “Control of the electronic properties of quasi-2D materials under biaxial strain”, was carried out at LPS in Orsay under the supervision of David Le Bolloc’h and Vincent Jacques. It addresses a central challenge in condensed matter physics: exploring and tuning material properties through external parameters.
An original approach to probe material properties
In the ongoing quest for new material properties with both fundamental and technological relevance, exploring phase diagrams as exhaustively as possible is essential. Traditionally, parameters such as temperature, pressure, magnetic and electric fields, or chemical doping are used to access different physical regimes.
More recently, the development of techniques enabling anisotropic mechanical strain has opened new directions, revealing a wide range of effects in electronic crystals.
It is within this framework that Antoine Gallo–Frantz’s work takes place.
A unique experimental setup
A central achievement of this thesis is the development of an original experimental device, designed and built at LPS, capable of applying uniaxial and biaxial strain to samples at cryogenic temperatures.
The device has a cross-shaped geometry and allows deformation along two perpendicular directions over a wide temperature range. It is mounted on a cryostat and topped with a PEEK dome transparent to X-rays, enabling in situ structural studies using X-ray diffraction.
Linking crystal structure and electronic properties
The broader goal of this work is to investigate the relationship between crystal structure and electronic properties, particularly in low-dimensional compounds exhibiting electronic instabilities such as charge density waves (CDWs).
To achieve this, the thesis combines:
- X-ray diffraction experiments (both laboratory-based and at large-scale facilities),
- electrical resistivity measurements.
This dual approach provides direct insight into both structural distortions and their electronic signatures, including transition temperatures.
Key results on TbTe₃
The study of the compound TbTe₃ reveals striking results:
- a modest strain applied along one crystallographic axis is sufficient to invert the in-plane lattice parameter ratio,
- this inversion induces a reorientation of the charge density wave,
- a coexistence regime emerges when the lattice parameters become equivalent.
These findings highlight the crucial role of mechanical strain in controlling electronic phases and open new avenues for tuning the properties of quantum materials.
Learn more
The prize winners present their work on the dedicated AFC webpage.
You can also find the full list of AFC PhD Thesis Prize recipients since 2009 in the “PhD Prize” section of the association’s website.