The quantum metric of electrons with spin-momentum locking.

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Title: The quantum metric of electrons with spin-momentum locking.
Authors: Sala, Giacomo, Mercaldo, Maria Teresa, Domi, Klevis, Gariglio, Stefano, Cuoco, Mario, Ortix, Carmine, Caviglia, Andrea D.
Source: Science. 8/21/2025, Vol. 389 Issue 6762, p822-825. 4p.
Subjects: Quantum mechanics, Electromagnetic fields, Wave functions, Antiferromagnetic materials, Calculus of tensors, Lanthanum
Abstract: Quantum materials are characterized by electromagnetic responses intrinsically linked to the geometry and topology of electronic wavefunctions that are encoded in the quantum metric and Berry curvature. Whereas Berry curvature–mediated transport effects have been identified in several magnetic and nonmagnetic systems, quantum metric–induced transport phenomena remain limited to topological antiferromagnets. Here, we show that spin-momentum locking, a general characteristic of the electronic states at surfaces and interfaces of spin-orbit–coupled materials, leads to a finite quantum metric. This metric activates a nonlinear in-plane magnetoresistance that we measured and electrically controlled in 111-oriented LaAlO3/SrTiO3 interfaces. These findings demonstrate the existence of quantum metric effects in a vast class of materials and enable previously unexplored strategies to design functionalities based on quantum geometry. Editor's summary: The quantum geometric tensor of a material provides insight into the topology and geometry of its electronic states. The real part of this tensor, the quantum metric, has so far been measured only in a limited number of materials. Sala et al. broadened this range of materials by predicting that spin-momentum locking of electronic states is associated with a finite quantum metric. The researchers experimentally verified this prediction by using 111-oriented lanthanum aluminate–strontium titanate (LaAlO3/SrTiO3) interfaces as a model system. —Jelena Stajic [ABSTRACT FROM AUTHOR]
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Database: Psychology and Behavioral Sciences Collection
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Abstract:Quantum materials are characterized by electromagnetic responses intrinsically linked to the geometry and topology of electronic wavefunctions that are encoded in the quantum metric and Berry curvature. Whereas Berry curvature–mediated transport effects have been identified in several magnetic and nonmagnetic systems, quantum metric–induced transport phenomena remain limited to topological antiferromagnets. Here, we show that spin-momentum locking, a general characteristic of the electronic states at surfaces and interfaces of spin-orbit–coupled materials, leads to a finite quantum metric. This metric activates a nonlinear in-plane magnetoresistance that we measured and electrically controlled in 111-oriented LaAlO3/SrTiO3 interfaces. These findings demonstrate the existence of quantum metric effects in a vast class of materials and enable previously unexplored strategies to design functionalities based on quantum geometry. Editor's summary: The quantum geometric tensor of a material provides insight into the topology and geometry of its electronic states. The real part of this tensor, the quantum metric, has so far been measured only in a limited number of materials. Sala et al. broadened this range of materials by predicting that spin-momentum locking of electronic states is associated with a finite quantum metric. The researchers experimentally verified this prediction by using 111-oriented lanthanum aluminate–strontium titanate (LaAlO3/SrTiO3) interfaces as a model system. —Jelena Stajic [ABSTRACT FROM AUTHOR]
ISSN:00368075
DOI:10.1126/science.adq3255