DQMP Forum - Felix Eder - Giacomo Sala

15.10.2024 13:00 – 14:00

Crystal Growth and Anisotropic Magnetic Properties of Incommensurately Modulated K1−xCrSe2 (x ≈ 0.13)
Felix Eder, Group of prof. von Rohr

Magnetic van der Waals materials receive growing interest, since their exfoliability down to the atomiclimit allows for the exploration of 2D magnetism. Using a mixed K/Se flux method, we were able to grow large single crystals of previously unknown under-stoichiometric K1–xCrSe2 (x ≈ 0.13). The basic structure of K1–xCrSe2 consists of the same structural features as K1–xCrSe2 [1]. However, as manifested by intense satellite reflections in single crystal X-ray diffraction measurements, it is incommensurately modulated (modulationvector q = 0.2675(4)a∗–0.1585(4)c∗). Magnetization measurements on oriented single crystals reveal strong magnetic anisotropy and transition at a much higher ordering tempera-ture than in KCrSe2.
In this talk, I will present how a slight compositional devia-tion in K-content leads to a very different crystal structure, a significant change in magnetic properties and incommensu-rate structural modulation, which can be explained by simple structure-chemical influences.
[1] C. van Bruggen, R. Haange, G. Wiegers, D. de Boer, Physica B+C 99, 166 (1980).


The Quantum Metric of Spin-momentum-locked Bands
Giacomo Sala, Group of prof. Caviglia

Electronic responses are governed by the geometry of electronic wavefunctions. These properties are encoded in the quantum metric and Berry curva-ture, which are respectively the real and imaginary parts of the quantum geometric tensor. In compar-ison to the Berry curvature, which has been probed in several physical systems, the quantum metric has rarely been observed [1-2]. Here [3], we theoret-ically predict and experimentally show that spin-momentum locking – a property of surfaces and in-terfaces of materials with spin-orbit coupling – is en-dowed with a finite quantum metric that activates a nonlinear magnetoresistance at the (111)-oriented LaAlO3/SrTiO3 interface. The concomitant detec-tion of the quantum metric and Berry curvature al-lows us to sense the full quantum geometric tensor in a nonmagnetic material. These findings reveal the importance of the quantum geometry for a vast class of materials.
[1] Gao, Science 381, 181 (2023).
[2] Wang, Nature 621, 487 (2023).
[3] Sala, in review.

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre