arXiv subjects

Nikolai Peshcherenko

Publications and source records attributed to Nikolai Peshcherenko.

12 recordsLinked to original sources

arXiv2026

Thickness-driven crossover from conventional to chiral nonreciprocal superconductivity in kagome metal CsV3Sb5

Superconductivity and its potential applications are governed by the symmetry of the superconducting order parameter. In the kagome metal CsV3Sb5, most bulk studies indicate conventional s-wave pairing. However, ultrathin flakes exhibit nonreciprocal transport, in particular a zero-field superconducting diode effect, which requires broken inversion and time-reversal symmetries. Here, using thickness dependent transport measurements, we observe the emergence of non-reciprocal second-harmonic magnetotransport signals and a zero-field superconducting diode effect, accompanied by a pronounced reduction of the out-of-plane coherence length with decreasing thickness. Upper critical field measurements further reveal a dimensional crossover from three-dimensional superconductivity in bulk to two-dimensional superconductivity in thin flakes. These findings indicate a thickness-induced chiral superconducting phase that breaks both inversion and time-reversal symmetries in the two-dimensional limit. Our work not only clarifies long-standing controversies regarding the pairing symmetry in CsV3Sb5, but also establishes thin-flake kagome superconductors as a versatile platform for engineering nonreciprocal quantum devices and exploring emergent topological phases.

cond-mat.supr-con↗

arXiv2026

Observation of the Magnus Nonlinear Hall effect from Chiral Weyl Monopoles

The nonlinear Hall effect (NLHE) connects crystalline symmetry to quantum geometry, offering a probe of band topology beyond linear transport. While most studies have focused on the Berry curvature dipole in low-symmetry crystals, mechanisms that directly probe Berry monopoles in higher-symmetry chiral lattices remain unexplored. Here, we report the observations of the NLHE in the chiral Weyl semimetal CoSi, a platform where the Berry curvature dipole is symmetry-forbidden. By employing focused ion beam-fabricated crossbar devices, we detect a robust second-harmonic Hall voltage under zero magnetic field, hosting all key signatures of the NLHE. Theoretical analysis attributes the nonlinear Hall conductivity to skew scattering of self-rotating electron wave packets, whose chirality is dictated by the underlying band topology, a process reminiscent of the classical Magnus effect. Furthermore, the NLHE signal exhibits a temperature-dependent sign reversal, and a strong, linearly field-dependent modulation that grows with carrier mobility, directly reflecting the topological Weyl nodes distribution near the Fermi level. These findings establish CoSi as a platform for Berry monopole-driven nonlinear transport, demonstrating a skew-scattering route to topological nonlinear Hall responses that bypasses conventional symmetry constraints.

cond-mat.mes-hall↗

arXiv2026

Programmable, Spontaneous Superlattice Memory in a Monolayer Topological Insulator

Memory is a foundational concept across disciplines, from neurobiology and electronics to artificial intelligence and quantum gravity. In materials, memory effects typically arise from ferroic orders, such as ferroelectricity and ferromagnetism, where information is stored in charge or spin degrees of freedom. Here, we report a surprising discovery of a nonvolatile superlattice memory effect in monolayer TaIrTe4, a dual quantum spin Hall insulator, where information is encoded through sharply contrasting lattice periodicities. In particular, in a pristine monolayer, we observe the spontaneous emergence of a long-period superlattice that can be programmed ON and OFF in a nonvolatile manner by electrostatic tuning of low-energy electronic states. This switching toggles the system between two structural configurations with unit cell areas differing by nearly two orders of magnitude. Mechanistically, our results reveal two independent and distinct instabilities, one in the lattice and the other in the QSH electrons, which are coupled, leading to electrostatic control of lattice configurations with nonvolatile memory. This finding is enabled by combining linear and nonlinear transport measurements, Raman spectroscopy, and scanning tunneling microscopy, which probe complementary aspects of the underlying orders. Remarkably, this nonvolatile memory effect stabilizes a spontaneous superlattice with a periodicity on the few-nanometer scale that remains robust across a wide doping range, persists over days, and survives above 70 K. Combined with the QSH topology, this stability offers a promising route to nonvolatile memory control of topological flat bands and their filling enabled quantum states. Our preliminary data indeed show the emergence of new insulating states at fractional superlattice fillings, which can be clearly switched ON and OFF together with the superlattice.

cond-mat.mes-hall↗

arXiv2026

Chiralometer: Direct Torque Detection of Crystal Chirality

Chirality governs phenomena ranging from chemical reactions to the topology of quasiparticle charge carriers. However, a direct macroscopic probe for crystal chirality remains a significant challenge, especially in time reversal symmetric systems with weak circular dichroism signal. Here, we propose the ``Chiralometer'', a mechanical detection method that probes chirality by driving angular momentum carriers out of equilibrium. Using first-principles calculations and semiclassical transport theory, we demonstrate that a temperature gradient in insulators or an electric field in metals induces uncompensated angular momentum in phonons and electrons, respectively. This imbalance generates a macroscopic mechanical torque ($τ\sim 10^{-11} N \cdot m$) well within the sensitivity of modern torque magnetometry and cantilever-based sensors. We identify robust signatures in chiral crystals such as Te, SiO$_2$, and the topological semimetal CoSi. Our work establishes mechanical torque as a fundamental order parameter for chirality, offering a transformative tool for orbitronics and chiral quantum materials.

cond-mat.mtrl-sci↗

arXiv2025

Efficient spin-pumping and spin transport across epitaxial Mn$_3$Sn(0001) noncollinear antiferromagnet/permalloy interfaces

The generation and control of spin currents are crucial for advancing next-generation spintronic technologies. These technologies depend on materials capable of efficiently sourcing and interconverting spin and charge currents, while overcoming some limitations associated with conventional ferromagnets and heavy metals. Kagome topological antiferromagnetic Weyl semimetals, such as Mn3Sn, present unique advantages owing to their distinct magnetic order and significant Berry curvature-driven transport phenomena. In this study, we systematically investigate spin current generation and spin-to-charge conversion phenomena in epitaxial (0001)-oriented Mn$_3$Sn thin films. Our findings reveal a spin Hall angle of 0.9$\%$ and a nearly isotropic in-plane spin Hall conductivity of ~44.4 ($\hbar$/e) $\Omega^{-1}$.cm$^{-1}$ at room temperature, originating from a combination of intrinsic and extrinsic contributions, as discussed in light of first-principle calculations. Furthermore, in Mn$_3$Sn(0001)/Ni$_{81}$Fe$_{19}$ heterostructures, we observe a high spin-mixing conductance of 28.52 nm$^{-2}$ and an interfacial spin-transparency of approximately 72$\%$. Notably, we also find that the spin diffusion length in Mn$_3$Sn(0001) epitaxial films exceeds 15 nm at room temperature. Our results highlight the potential, and limitations, of the topological Weyl noncollinear antiferromagnet Mn$_3$Sn as an efficient material for spin transport and conversion in prospective spintronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Universal giant spin Hall effect in moire metal

While moiré phenomena have been extensively studied in low-carrier-density systems such as graphene and semiconductors, their implications for metallic systems with large Fermi surfaces remain largely unexplored. Using GPU-accelerated large-scale ab-initio quantum transport simulations, we investigate spin transport in two distinct platforms: twisted bilayer MoTe$_2$ (semiconductor, from lightly to heavily doping) and NbX$_2$ ($X$ = S, Se; metals). In twisted MoTe$_2$, the spin Hall conductivity (SHC) evolves from $4\tfrac{e}{4π}$ at $5.09^\circ$ to $10\tfrac{e}{4π}$ at $1.89^\circ$, driven by the emergence of multiple isolated Chern bands. Remarkably, in heavily doped metallic regimes--without isolated Chern bands--we observe a universal amplification of the spin Hall effect from Fermi surface reconstruction under long-wavelength potential, with the peak SHC tripling from $6\tfrac{e}{4π}$ at $5.09^\circ$ to $17\tfrac{e}{4π}$ at $3.89^\circ$. For prototypical moiré metals like twisted NbX$_2$, we identify a record SHC of $-17\tfrac{e}{4π}$ (-5200 $(\hbar / e)S/cm$ in 3D units), surpassing all known bulk materials. These results establish moiré engineering as a powerful strategy for enhancing spin-dependent transport, and advancing ab-initio methodologies to bridge atomic-scale precision with device-scale predictions in transport simulations.

cond-mat.mes-hall↗

arXiv2025

Chiral superconductivity from spin polarized Chern band in twisted MoTe$_2$

Superconductivity has been observed in twisted MoTe2 within the anomalous Hall metal parent state. Key signatures-including a fully spin/valley polarized normal state, anomalous Hall resistivity hysteresis, superconducting phase adjacent to the fractional Chern insulating state and a narrow superconducting dome at zero gating field-collectively indicate chiral superconductivity driven by intravalley pairing of electrons. Within the Kohn-Luttinger mechanism, we compute the superconducting phase diagram via random phase approximation, incorporating Coulomb repulsion in a realistic continuum model. Our results identify a dominant intravalley pairing with a narrow superconducting dome of p+ip type at zero gate field. This chiral phase contrasts sharply with the much weaker time-reversal-symmetric intervalley pairing at finite gating field. Our work highlights the role of band topology in achieving robust topological superconductivity, and supports the chiral and topological nature of the superconductivity observed in twisted MoTe2.

cond-mat.supr-con↗

arXiv2024

Interplay between topology and correlations in the second moiré band of twisted bilayer MoTe2

Topological flat bands formed in two-dimensional lattice systems offer unique opportunity to study the fractional phases of matter in the absence of an external magnetic field. Celebrated examples include fractional quantum anomalous Hall (FQAH) effects and fractional topological insulators. Recently, FQAH effects have been experimentally realized in both the twisted bilayer MoTe2 (tMoTe2) system and the rhombohedral stacked multilayer graphene/hBN moiré systems. To date, experimental studies mainly focus on the first moiré flat band, except a very recent work that studied novel transport properties in higher moiré bands of a 2.1° tMoTe2 device. Here, we present the systematical transport study of approximately 3° tMoTe2 devices, especially for the second moiré band. At ν = -2 and -4, time-reversal-symmetric single and double quantum spin Hall states formed, consistent with the previous observation in 2.1° tMoTe2 device. On the other hand, we observed ferromagnetism in the second moiré band, and a Chern insulator state driven by out-of-plane magnetic fields at ν = -3. At ν = -2.2 to -2.7, finite temperature resistivity minimum with 1/T scaling at low temperatures, and large out-of-plane negative magnetoresistance have been observed. Applying out-of-plane electric field can induce quantum phase transitions at both integer and fractional filling factors. Our studies pave the way for realizing tunable topological states and other unexpected magnetic phases beyond the first moiré flat band based on twisted MoTe2 platform.

cond-mat.mes-hall↗

arXiv2024

Quantized nonlinear Hall effect from chiral monopole

Nonlinear Hall effect arises in materials without inversion symmetry, and the intrinsic contribution is typically from Berry curvature dipole of non-universal Fermi pockets. Here we propose that nonlinear Hall effect can reach quantization in chiral Weyl semimetals without mirror symmetries. The energy shift between a pair of Weyl nodes leads to chirally asymmetric intra-node relaxation, and the net trace of nonlinear Hall conductivity is thus quantized in units of $e^3/\hbar^2$ and determined by sum of monopole charge weighted by the transport relaxation time. Our theory also applies to mirror symmetric Weyl/Dirac semimetals with chiral anomaly. Additionally, besides DC transport probes, we anticipate that nonlinear circular dichroism measurements could detect chiral asymmetry-induced currents.

cond-mat.str-el↗

arXiv2024

Sublinear transport in Kagome metals: Interplay of Dirac cones and Van Hove singularities

Kagome metals are known to host Dirac fermions and saddle point Van Hove singularities near Fermi level. With the minimal two-pocket model (Dirac cone + Van Hove singularity), we propose a semiclassical theory to explain the experimentally observed sublinear resistivity in Ni$_3$In and other Kagome metals. We derive the full semiclassical description of kinetic phenomena using Boltzmann equation, and demonstrate that internode electron-electron interaction leads to sublinear in $T$ scaling for both electrical and thermal transport at low temperatures. At higher temperatures above the Dirac node chemical potential, thermal and electric current dissipate through distinct scattering channels, making a ground for Wiedemann-Franz law violation.

cond-mat.str-el↗

arXiv2023

Wannier functions, minimal model and charge transfer in Pb$_9$CuP$_6$O$_{25}$

Recent preprints claimed that the copper doped lead apatite Pb$_9$CuP$_6$O$_{25}$ (LK99) might be a high-temperature superconductor because of its strong diamagnetism and transport properties. Motivated by the strongly correlated effects that can arise from a triangular lattice of Cu atoms with narrow bandwidth, we calculated the maximally projected Wannier functions from density functional theory simulations, and constructed a minimal two-orbital triangular model with Cu ($3d_{xz},3d_{yz}$) basis, and a four-orbital buckled honeycomb model with Cu ($3d_{xz},3d_{yz}$), O ($2p_x,2p_y$). Since the Coulomb interaction Ud is much larger than potential energy difference between Cu and O, charge transfer will occur for hole filling fraction $n_h > 1$. We further calculate the interaction parameters, and discuss the possible insulating state and corresponding spin exchange coupling.

cond-mat.supr-con↗

arXiv2023

Universal sublinear resistivity in vanadium kagome materials hosting charge density waves

The recent discovery of a charge density (CDW) state in ScV$_6$Sn$_6$ at $T_{\textrm{CDW}}$ = 91 K offers new opportunities to understand the origins of electronic instabilities in topological kagome systems. By comparing to the isostructural non-CDW compound LuV$_6$Sn$_6$, we unravel interesting electrical transport properties in ScV$_6$Sn$_6$, above and below the charge ordering temperature. We observed that by applying a magnetic field along the $a$ axis, the temperature behavior of the longitudinal resistivity in ScV$_6$Sn$_6$ changes from metal-like to insulator-like above the CDW transition. We show that in the charge ordered state ScV$_6$Sn$_6$ follows the Fermi liquid behavior while above that, it transforms into a non-Fermi liquid phase in which the resistivity varies sublinearly over a broad temperature range. The sublinear resistivity, which scales by $T^{3/5}$ is a common feature among other vanadium-containing kagome compounds exhibiting CDW states such as KV$_3$Sb$_5$, RbV$_3$Sb$_5$, and CsV$_3$Sb$_5$. By contrast, the non-Fermi liquid behavior does not occur in LuV$_6$Sn$_6$. We explain the $T^{3/5}$ universal scaling behavior from the Coulomb scattering between Dirac electrons and Van Hove singularities; common features in the electronic structure of kagome materials. Finally, we show anomalous Hall-like behavior in ScV$_6$Sn$_6$ below $T_{\textrm{CDW}}$, which is absent in the Lu compound. Comparing the transport properties of ScV$_6$Sn$_6$ and LuV$_6$Sn$_6$ is valuable to highlight the impacts of the unusual CDW in the Sc compound.

cond-mat.str-el↗