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1. Dirac-fermion-assisted interfacial superconductivity in epitaxial topological-insulator/iron-chalcogenide heterostructures

   https://doi.org/10.1038/s41467-023-42902-2  

   Yi, Hemian; Hu, Lun-Hui; Zhao, Yi-Fan; Zhou, Ling-Jie; Yan, Zi-Jie; Zhang, Ruoxi; Yuan, Wei; Wang, Zihao; Wang, Ke; Hickey, Danielle Reifsnyder; et al (December 2023, Nature Communications)

   Over the last decade, the possibility of realizing topological superconductivity (TSC) has generated much excitement. TSC can be created in electronic systems where the topological and superconducting orders coexist, motivating the continued exploration of candidate material platforms to this end. Here, we usemolecular beam epitaxy (MBE) to synthesize heterostructures that host emergent interfacial superconductivity when a non-superconducting antiferromagnet (FeTe) is interfaced with a topological insulator (TI) (Bi, Sb)2Te3. By performing in-vacuo angle-resolved photoemission spectroscopy (ARPES) and ex-situ electrical transport measurements, we find that the superconducting transition temperature and the upper critical magnetic field are suppressed when the chemical potential approaches the Dirac point. We provide evidence to show that the observed interfacial superconductivity and its chemical potential dependence is the result of the competition between the Ruderman-Kittel-Kasuya-Yosida-type ferromagnetic coupling mediated by Dirac surface states and antiferromagnetic exchange couplings that generate the bicollinear antiferromagnetic order in the FeTe layer. 

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2. Meissner Effect and Nonreciprocal Charge Transport in Non‐Topological 1T‐CrTe ₂ /FeTe Heterostructures

   https://doi.org/10.1002/adma.202520598  

   Yan, Zi‐Jie; Chan, Ying‐Ting; Yuan, Wei; Wang, Annie G; Yi, Hemian; Wang, Zihao; Zhou, Lingjie; Rong, Hongtao; Zhuo, Deyi; Wang, Ke; et al (March 2026, Advanced Materials)

   ABSTRACT Interface‐induced superconductivity has recently been achieved by stacking a magnetic topological insulator layer on an antiferromagnetic FeTe layer. However, the mechanism driving this emergent superconductivity remains unclear. Here, we employ molecular beam epitaxy to grow a 1T‐CrTe₂layer, a 2D ferromagnet with a Curie temperature up to room temperature, on a FeTe layer. These 1T‐CrTe₂/FeTe heterostructures show superconductivity with a critical temperature of ∼12 K. Through magnetic force microscopy measurements, we observe the Meissner effect on the surface of the 1T‐CrTe₂layer. Our electrical transport measurements reveal that the 1T‐CrTe₂/FeTe heterostructures exhibit nonreciprocal charge transport behavior, characterized by a large magneto‐chiral anisotropy coefficient. The enhanced nonreciprocal charge transport in 1T‐CrTe₂/FeTe heterostructures provides a promising platform for exploring the magnetically controllable superconducting diode effect. 

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3. Detecting topological superconductivity via Berry curvature effects in spectral functions

   https://doi.org/10.1103/PhysRevB.111.064508  

   Liao, Yunxiang; Hsu, Yi-Ting (February 2025, Physical Review B)

   Experimental efforts on topological superconductivity (TSC) have primarily focused on the detection of Majorana boundary modes, while the bulk properties of TSC, particularly in two dimensions, remain relatively underexplored. In this work, we theoretically propose a distinctive signature in the spectral function away from the boundaries, capable of detecting two-dimensional (2D) chiral 𝑝-wave TSC induced in a Rashba spin-orbit-coupled heterostructure. This signature can be probed experimentally through angle-resolved photoemission spectroscopy or momentum- and energy-resolved tunneling spectroscopy under a weak magnetic field 𝐵. We show that within the topological phase, the spectral intensity of the lowest superconducting band at small momenta 𝑘∼0 brightens (darkens) linearly with increasing 𝐵, whereas it darkens (brightens) in the trivial phase when the Rashba system is electron (hole) doped. This sharp contrast arises from the phase-space Berry curvature (BC) of Bogoliubov quasiparticles, a novel quantum geometric property that generalizes the conventional momentum-space BC. The effect of this phase-space BC can also be detected by the differential conductance away from the boundaries. Our falsifiable prediction provides an experimental avenue for detecting Rashba-induced chiral 𝑝-wave TSC without relying on Majorana mode detection, addressing a key challenge in the realization of 2D TSC. 

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4. Enhanced ferromagnetism in monolayer Cr ₂ Te ₃ via topological insulator coupling

   https://doi.org/10.1088/1361-6633/add9c5  

   Ou, Yunbo; Mirzhalilov, Murod; Nemes, Norbert M; Martinez, Jose L; Rocci, Mirko; Duong, Alexander; Akey, Austin; Foucher, Alexandre C; Ge, Wenbo; Suri, Dhavala; et al (May 2025, Reports on Progress in Physics)

   Abstract Exchange-coupled interfaces are pivotal in exploiting two-dimensional (2D) ferromagnetism. Due to the extraordinary correlations among charge, spin, orbital and lattice degrees of freedom, layered magnetic transition metal chalcogenides (TMCs) bode well for exotic topological phenomena. Here we report the realization of wafer-scale Cr₂Te₃down to monolayer (ML) on insulating SrTiO₃(111) and/or Al₂O₃(001) substrates using molecular beam epitaxy. Robust ferromagnetism persists in the 2D limit. In particular, the Curie temperatureT_Cof 2 ML Cr₂Te₃increases from 100 K to ∼120 K when proximitized to topological insulator (TI) (Bi,Sb)₂Te₃, with substantially boosted magnetization as observed via polarized neutron reflectometry. Our experiments and theory strongly indicate that the Bloembergen–Rowland interaction is likely universal underlyingT_Cenhancement in TI-coupled magnetic heterostructures. The topological-surface-enhanced magnetism in 2D TMC enables further exchange coupling physics and quantum hybrid studies, including paving the way to realize interface-modulated topological electronics. 

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5. Topological superconductor candidates PdBi2Te4 and PdBi2Te5 from a generic ab initio strategy

   https://doi.org/10.1038/s41524-023-01144-y  

   Luo, Aiyun; Li, Ying; Qin, Yi; Hu, Jingnan; Wang, Xiaoxu; Zou, Jinyu; Lian, Biao; Xu, Gang (December 2023, npj Computational Materials)

   Abstract Superconducting topological metals (SCTMs) have recently emerged as a promising platform of topological superconductivity (TSC) and Majorana zero modes for quantum computation. Despite their importance in both fundamental research and applications, SCTMs are very rare in nature. Here, we propose a strategy to design SCTMs by intercalating the superconducting units into the topological insulators. A program that characterizes the superconducting BdG Chern number of 2D BdG Hamiltonian from ab initio calculations is also developed. Following this strategy, PdBi₂Te₅and PdBi₂Te₄are found to be experimentally synthesizable and ideal SCTMs. Chiral TSC could be realized in such SCTMs by incorporating topological surface states with Zeeman effect, which can be realized by an external magnetic field or in proximity to ferromagnetic insulator. Our strategy provides a new method for identifying the SCTMs and TSC candidates, and the program makes it possible to design and modulate the TSC candidates from ab initio calculations. 

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