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1. Thermoelectric transport at F4TCNQ–silicon interface

   https://doi.org/10.1063/1.5050537  

   Liu, Naiming; Peters, Jonathan; Ramu, Ashok; Floro, Jerrold_A; Bowers, John_E; Zebarjadi, Mona (February 2019, APL Materials)

   Hybrid organic-inorganic materials are among the latest class of materials proposed for thermoelectric applications. The organic-inorganic interface is critical in determining the effective transport properties of the hybrid material. We study the thermoelectric properties of the tetrafluoro-tetracyanoquinodimethane (F4TCNQ)–silicon interface. Transfer of electrons from silicon to F4TCNQ results in holes trapped within the screening length of the interface that can move parallel to the interface. We measure the response of these trapped charges to applied temperature differential and compare the thermoelectric transport properties of the silicon with and without F4TCNQ. The results confirm the presence of interface charges and demonstrate an enhanced interface thermoelectric power factor. These outcomes of this study could be used in designing 3D hybrid structures with closely packed interfaces to replicate a bulk thermoelectric material. 

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2. Substrate effects in hysteresis of microscale Ni–Mn–Sn Heusler alloy films

   https://doi.org/10.1063/5.0159129  

   Zhang, Yijia; Zhao, Dexin; Lago, Juan C; Xie, Kelvin; Shamberger, Patrick J (August 2023, Applied Physics Letters)

   During martensitic phase transformations in thin films, substrates impact hysteresis by introducing an additional interface, which can inhibit martensite/austenite interface motion. In order to reduce hysteresis, we examine 2.9–14.5 μm thick Ni–Mn–Sn films, which in some cases have been delaminated from the substrates before or after annealing. We compare thermal hysteresis and defect densities at the interface. Delaminating films prior to annealing decreases hysteresis, whereas delaminating films after annealing does not significantly impact hysteresis. Substrate effects are attributed to the thermal expansion mismatch between the film and substrate, resulting in the formation of dislocations at the interface and, consequentially, an increase in frictional resistance to martensite/austenite interface motion. 

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3. Asymmetric fluctuations and self-folding of active interfaces

   https://doi.org/10.1073/pnas.2410345121  

   Zhao, Liang; Gulati, Paarth; Caballero, Fernando; Kolvin, Itamar; Adkins, Raymond; Marchetti, M_Cristina; Dogic, Zvonimir (December 2024, Proceedings of the National Academy of Sciences)

   We study the structure and dynamics of the interface separating a passive fluid from a microtubule-based active fluid. Turbulent-like active flows power giant interfacial fluctuations, which exhibit pronounced asymmetry between regions of positive and negative curvature. Experiments, numerical simulations, and theoretical arguments reveal how the interface breaks up the spatial symmetry of the fundamental bend instability to generate local vortical flows that lead to asymmetric interface fluctuations. The magnitude of interface deformations increases with activity: In the high activity limit, the interface self-folds invaginating passive droplets and generating a foam-like phase, where active fluid is perforated with passive droplets. These results demonstrate how active stresses control the structure, dynamics, and break-up of soft, deformable, and reconfigurable liquid–liquid interfaces. 

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4. Signatures of a spin-active interface and a locally enhanced Zeeman field in a superconductor-chiral material heterostructure

   https://doi.org/10.1126/sciadv.ado4875  

   Chen, Cliff; Tran, Jason; McFadden, Anthony; Simmonds, Raymond; Saito, Keisuke; Chu, En-De; Morales, Daniel; Suezaki, Varrick; Hou, Yasen; Aumentado, Joe; et al (August 2024, Science Advances)

   A localized Zeeman field, intensified at heterostructure interfaces, could play a crucial role in a broad area including spintronics and unconventional superconductors. Conventionally, the generation of a local Zeeman field is achieved through magnetic exchange coupling with a magnetic material. However, magnetic elements often introduce defects, which could weaken or destroy superconductivity. Alternatively, the coupling between a superconductor with strong spin-orbit coupling and a nonmagnetic chiral material could serve as a promising approach to generate a spin-active interface. Here, we leverage an interface superconductor, namely, induced superconductivity in noble metal surface states, to probe the spin-active interface. Our results unveil an enhanced interface Zeeman field, which selectively closes the surface superconducting gap while preserving the bulk superconducting pairing. The chiral material, i.e., trigonal tellurium, also induces Andreev bound states (ABS) exhibiting spin polarization. The field dependence of ABS manifests a substantially enhanced interface Landég-factor (g_eff~ 12), thereby corroborating the enhanced interface Zeeman energy. 

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5. Analysis and finite element approximation of a diffuse interface approach to the Stokes–Biot coupling

   https://doi.org/10.1093/imanum/draf002  

   Aznaran, Francis_R_A; Bukač, Martina; Muha, Boris; Salgado, Abner_J (March 2025, IMA Journal of Numerical Analysis)

   Abstract We consider the interaction between a poroelastic structure, described using the Biot model in primal form, and a free-flowing fluid, modelled with the time-dependent incompressible Stokes equations. We propose a diffuse interface model in which a phase field function is used to write each integral in the weak formulation of the coupled problem on the entire domain containing both the Stokes and Biot regions. The phase field function continuously transitions from one to zero over a diffuse region of width $$\mathcal{O}(\varepsilon)$$ around the interface; this allows the weak forms to be integrated uniformly across the domain, and obviates tracking the subdomains or the interface between them. We prove convergence in weighted norms of a finite element discretization of the diffuse interface model to the continuous diffuse model; here the weight is a power of the distance to the diffuse interface. We, in turn, prove convergence of the continuous diffuse model to the standard, sharp interface, model. Numerical examples verify the proven error estimates, and illustrate application of the method to fluid flow through a complex network, describing blood circulation in the circle of Willis. 

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