arXiv subjects

Digambar A. Jangade

Publications and source records attributed to Digambar A. Jangade.

6 recordsLinked to original sources

arXiv2026

Quantum interference in a twisted high-Tc SQUID senses emergent interfacial order

Engineering artificial systems by twisting and stacking van der Waals materials has proven to be an excellent platform for exploring emergent quantum phenomena that can be significantly different from the constituents. Recent advances in the fabrication of high-quality twisted interfaces provide a unique opportunity to study the little-explored interfacial superconducting order in twisted cuprate superconductors. In our work, we fabricate superconducting quantum interference devices (SQUID) that utilize the twisted interface of $\mathrm{Bi_2Sr_2CaCu_2O_{8+δ}}$, a high-Tc cuprate superconductor. By measuring the magnetic field modulation of switching current and differential resistance, we find a $\mathrmπ$ phase difference between the two Josephson junction arms of the SQUID reflecting chiral superconducting order -- a crucial aspect inaccessible to single Josephson junction devices of the past. Our observations also indicate co-tunneling of the Cooper pairs and a time-reversal symmetry-broken emergent superconducting order. Additionally, these SQUIDs are well suited for use as state-of-the-art flux sensors close to 77 K, achieving a flux noise sensitivity of $\sim$1.5 $\mathrm{μΦ_0/\sqrt{Hz}}$. Stabilizing new superconducting orders using twisted interfaces and probing them using quantum interference opens new avenues to understanding the microscopic origin of unconventional superconductors. Our SQUID architecture is suitable for investigating the charge transport mechanisms and the symmetry of superconducting order at the interfaces of other systems, reflecting the broad applicability beyond cuprate superconductors.

cond-mat.supr-con↗

arXiv2025

Modulation of quantum geometry and its coupling to pseudo-electric field by dynamic strain

Two-dimensional materials are a fertile ground for exploring quantum geometric phenomena, with Berry curvature and its first moment, the Berry curvature dipole, playing a central role in their electronic response. These geometric properties influence electronic transport and result in the anomalous and nonlinear Hall effects, and are typically controlled using static electric fields or strain. However, the possibility of modulating quantum geometric quantities in real-time remains unexplored. Here, we demonstrate the dynamic modulation of Berry curvature and its moments, as well as the generation of a pseudo-electric field using time-dependent strain. By placing heterostructures on a membrane, we introduce oscillatory strain together with an in-plane AC electric field and measure Hall signals that are modulated at linear combinations of the frequencies of strain and electric field. Our measurements reveal modulation of Berry curvature and its first moment. Notably, we provide direct experimental evidence of pseudo-electric field that results in an unusual dynamic strain-induced Hall response. This approach opens up a new pathway for controlling quantum geometry on demand, moving beyond conventional static perturbations. The pseudo-electric field provides a framework for external electric field-free anomalous Hall response and opens new avenues for probing the topological properties.

cond-mat.mes-hall↗

arXiv2024

Pick-up and assembling of chemically sensitive van der Waals heterostructures using dry cryogenic exfoliation

Assembling atomic layers of van der Waals materials (vdW) combines the physics of two materials, offering opportunities for novel functional devices. Realization of this has been possible because of advancements in nanofabrication processes which often involve chemical processing of the materials under study; this can be detrimental to device performance. To address this issue, we have developed a modified micro-manipulator setup for cryogenic exfoliation, pick up, and transfer of vdW materials to assemble heterostructures. We use the glass transition of a polymer PDMS to cleave a flake into two, followed by its pick-up and drop to form pristine twisted junctions. To demonstrate the potential of the technique, we fabricated twisted heterostructure of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO), a van der Waals high-temperature cuprate superconductor. We also employed this method to re-exfoliate NbSe$_2$ and make twisted heterostructure. Transport measurements of the fabricated devices indicate the high quality of the artificial twisted interface. In addition, we extend this cryogenic exfoliation method for other vdW materials, offering an effective way of assembling heterostructures and twisted junctions with pristine interfaces.

cond-mat.mes-hall↗

arXiv2023

High-temperature Josephson diode

Symmetry plays a critical role in determining various properties of a material. Semiconducting p-n junction diode exemplifies the engineered skew electronic response and is at the heart of contemporary electronic circuits. The non-reciprocal charge transport in a diode arises from doping-induced breaking of inversion symmetry. Breaking of time-reversal, in addition to inversion symmetry in some superconducting systems, leads to an analogous device - the superconducting diode. Following the pioneering first demonstration of the superconducting diode effect (SDE), a plethora of new systems showing similar effects have been reported. SDE lays the foundation for realizing ultra-low dissipative circuits, while Josephson phenomena-based diode effect (JDE) can enable realization of protected qubits. However, SDE and JDE reported thus far are at low temperatures ($\sim$ 4 K or lower) and impede their adaptation to technological applications. Here we demonstrate a Josephson diode working up to 77 K using an artificial Josephson junction (AJJ) of twisted layers of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO). The non-reciprocal response manifests as an asymmetry in the magnitude of switching currents and their distributions and appears for all twist angles. The asymmetry is induced by and tunable with a very small magnetic field applied perpendicular to the junction. We report a record asymmetry of 60 % at 20 K. We explain our results within a vortex-based scenario. Our results provide a path toward realizing superconducting quantum circuits at liquid nitrogen temperature.

cond-mat.supr-con↗

arXiv2023

Nanowire bolometer using a 2D high-temperature superconductor

Superconducting nanowires are very important due to their applications ranging from quantum technology to astronomy. In this work, we implement a non-invasive process to fabricate nanowires of high-$T_\text{c}$ superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO). We demonstrate that our nanowires can be used as bolometers in the visible range with very high responsivity of 9.7 $\times$ 10$^{3}$ V/W. Interestingly, in a long (30 $μ$m) nanowire of 9 nm thickness and 700 nm width, we observe bias current-dependent localized spots of maximum photovoltage. Moreover, the scalability of the bolometer responsivity with the normal state resistance of the nanowire could allow further performance improvement by increasing the nanowire length in a meander geometry. We observe phase slip events in nanowires with small cross-sections (12 nm thick, 300 nm wide, and 3 $μ$m long) at low temperatures. Our study presents a scalable method for realizing sensitive bolometers working near the liquid-nitrogen temperature.

cond-mat.supr-con↗

arXiv2020

On-demand local modification of high-$T_\text{c}$ superconductivity in few unit-cell thick Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$

High-temperature superconductors (HTS) are important for potential applications and for understanding the origin of strong correlations. Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit-cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science. Similarly, modifying superconductivity in HTS locally, on a small length scale, will be of immense interest for superconducting electronics. Here we report transport studies on few unit-cell thick BSCCO and modify its superconductivity locally by depositing metal on the surface. Deposition of chromium (Cr) on the surface over a selected area of BSCCO results in insulating behavior of the patterned region. Cr locally depletes oxygen in CuO$_2$ planes and disrupts the superconductivity in the layers below. Our technique of modifying superconductivity is suitable for making sub-micron superconducting wires and more complex superconducting electronic devices.

cond-mat.supr-con↗