Subarna Das

Humboldt Fellow as of Juni 2026

Overview of my research project:

The anomalous Hall and Nernst effects reveal how magnetic symmetry and Berry curvature influence electrical and thermoelectric transport in solids. Large responses in non-collinear antiferromagnets,  espite their small net magnetization, show that transverse transport is not governed by magnetization  lone. Chiral spin fluctuations can also contribute to Hall and Nernst signals. My research investigates how the symmetry of these fluctuations affects transport in the absence of long-range magnetic order. The focus is on frustrated kagome metals and the interplay between nematicity and scalar spin chirality. Nematicity describes spontaneous rotational symmetry breaking without loss of translational symmetry, whereas scalar spin chirality captures the handedness of noncoplanar spin configurations. I will investigate whether nematic correlations can influence chiral spin fluctuations and their contribution to Hall and Nernst responses. The aim is to search for nematic-chiral liquid states in which symmetry-breaking spin correlations persist without long-range ordering of the magnetic moments.
As a Humboldt Fellow, I will combine single-crystal growth and microdevice fabrication with electrical and thermoelectric transport measurements. Alongside Hall and Nernst measurements across magnetic transitions, I will examine in-plane resistivity and thermopower anisotropy for signatures of nematic correlations. Complementary probes of magnetism and spin dynamics, together with theoretical modelling, will help relate transport anomalies to the underlying spin correlations. A second part of the project will examine how uniaxial strain modifies spin correlations and their transport signatures. Strain provides a  controlled way to perturb lattice and magnetic symmetries. I will study its influence across magnetic phase boundaries, including regimes above the ordering temperature, and map the evolution of Hall and  Nernst responses with temperature, magnetic field and strain. These experiments will test whether fluctuation-driven transverse transport can be tuned or switched reversibly.
This research will be carried out in Prof. Claudia Felser’s group at the Max Planck Institute for Chemical Physics of Solids in Dresden. Prof. Felser’s pioneering contributions to topological quantum materials, particularly magnetic Weyl semimetals and non-collinear antiferromagnets, have helped to establish the relationship between magnetic symmetry, electronic topology and unconventional transport. Her  extensive expertise in solid-state chemistry and the design and discovery of quantum materials is directly relevant to the selection and investigation of the frustrated kagome metals in this project. Working  with Prof. Felser and her team will allow me to combine my background in electrical and thermal transport with this breadth of expertise to investigate how nematicity and spin chirality influence transverse transport in the absence of long-range magnetic order.