arXiv subjects

A. Dal Din

Publications and source records attributed to A. Dal Din.

4 recordsLinked to original sources

arXiv2026

Discerning ground state and photoemission-induced spin textures in altermagnetic $α$-MnTe

The recently discovered class of altermagnets provide a physical realization of an unconventional compensated magnetic phase with a higher partial-wave type of ordering, reminiscent of unconventional superfluid phases. Their stability under normal conditions has sparked significant research interest, spanning fields from spintronics to topological and correlated quantum materials. Spin- and angle-resolved photoemission spectroscopy (SARPES) has great promise to resolve the momentum-dependent spin textures, which are intricately interweaved with the altermagnetic direct space spin order. Using the relativistic $d$-wave-like collinear spin polarization on one of the non-relativistic nodal surfaces of the altermagnetic band structure of $α$-MnTe as an example, we here identify and resolve the challenges associated with (S)ARPES studies on altermagnets. We focus particularly on the role of photoemission-induced electron polarization and the coupling between light and the Néel vector of a magnetic domain. Our findings reveal an atypical behaviour of photoemission selection rules while using linearly-polarized light. Our methods allow to distinguish polarization of photoelectrons originating from the sample's ground state spin texture, on one hand, and from the photoemission process, on the other hand. Our experimental results are supported by a combination of ab initio band-structure and 1-step photoemission calculations.

cond-mat.str-el↗

arXiv2025

Unconventional relativistic spin polarization of electronic bands in an altermagnet

Altermagnetism is a recently identified phase with a d, g or i-wave spin symmetry of magnetic ordering. Its discovery opens new research fronts at intersections of magnetism and spintronics with fields ranging from superconductivity to topological and relativistic quantum physics. Here we demonstrate an unconventional relativistic spin polarization in an altermagnet by spin and angle resolved photoemission spectroscopy of electronic bands in single-domain MnTe. The relativistic spin-orbit coupling origin is revealed by observing that the alternating momentum-dependent spin polarization is orthogonal to the magnetic-ordering vector. The collinearity, even-parity and time-reversal-odd nature of the demonstrated relativistic spin polarization in the altermagnet is unparalleled in conventional forms of the relativistic spin polarization. Our experimental results and methodology are supported by non-relativistic spin-symmetry and relativistic magnetic-symmetry analyses, and microscopic ab initio ground-state and photoemission theory.

cond-mat.mes-hall↗

arXiv2024

Altermagnetism imaged and controlled down to the nanoscale

Nanoscale detection and control of the magnetic order underpins a broad spectrum of fundamental research and practical device applications. The key principle involved is the breaking of time-reversal ($\cal{T}$) symmetry, which in ferromagnets is generated by an internal magnetization. However, the presence of a net-magnetization also imposes severe limitations on compatibility with other prominent phases ranging from superconductors to topological insulators, as well as on spintronic device scalability. Recently, altermagnetism has been proposed as a solution to this restriction, since it shares the enabling $\cal{T}$-symmetry breaking characteristic of ferromagnetism, combined with the antiferromagnetic-like vanishing net-magnetization. To date, altermagnetic ordering has been inferred from spatially averaged probes. Here, we demonstrate nanoscale imaging and control of altermagnetic ordering ranging from nanoscale vortices to domain walls to microscale single-domain states in MnTe. We combine the $\cal{T}$-symmetry breaking sensitivity of X-ray magnetic circular dichroism with magnetic linear dichroism and photoemission electron microscopy, to achieve detailed imaging of the local altermagnetic ordering vector. A rich variety of spin configurations can be imposed using microstructure patterning or thermal cycling in magnetic fields. The demonstrated detection and control of altermagnetism paves the way for future research ranging from ultra-scalable digital and neuromorphic spintronic devices, to the interplay of altermagnetism with non-dissipative superconducting or topological phases.

cond-mat.mtrl-sci↗

arXiv2024

X-ray Magnetic Circular Dichroism in Altermagnetic $α$-MnTe

Altermagnetism is a recently identified magnetic symmetry class combining characteristics of conventional collinear ferromagnets and antiferromagnets, that were regarded as mutually exclusive, and enabling phenomena and functionalities unparalleled in either of the two traditional elementary magnetic classes. In this work we use symmetry and ab initio theory to explore X-ray magnetic circular dichroism (XMCD) in the altermagnetic class. Our results highlight the distinct phenomenology in altermagnets of this time-reversal symmetry breaking response, and its potential utility for element-specific spectroscopy and microscopy in altermagnets. As a representative material for our XMCD study we choose $α$-MnTe with the compensated antiparallel magnetic order in which an anomalous Hall effect has been already demonstrated both in theory and experiment. The predicted magnitude of XMCD lies well within the resolution of existing experimental techniques.

cond-mat.mtrl-sci↗