arXiv subjects

Shangjie Tian

Publications and source records attributed to Shangjie Tian.

At least 19 recordsLinked to original sources

arXiv2026

Physical properties of RhGe and CoGe single crystals synthesized under high pressure

Chiral topological semimetals hosting multifold fermions and exotic surface states represent a frontier in topological materials research. Among them, noncentrosymmetric cubic B20 compounds-notably transition-metal silicides and germanides-offer a unique platform for realizing symmetry-protected topological phases and unconventional optoelectronic responses. Here, we report the physical properties of RhGe and CoGe single crystals with B20 structure in detail. Transport measurements reveal metallic behavior with characteristic Fermi-liquid scaling at low temperatures, while magnetization results confirm paramagnetism in both compounds. In addition, both of materials exhibit low carrier concentrations with small electronic specific heat coefficient, indicating their semimetal feature with weak electronic correlations. Such high-quality CoGe and RhGe single crystals provide a material platform to explore the evolution of multifold fermions and the instability of helicoid-arc surface states with spin-orbit coupling and surface environment in B20 material systems.

cond-mat.str-el↗

arXiv2026

Pressure-induced superconductivity in topological insulator Ge2Bi2Te5 and the evolution with Mn doping

Introducing superconductivity (SC) or magnetism into topological insulators (TIs) can give rise to novel quantum states and exotic physical phenomena. Here, we report a high-pressure transport study on the TI Ge2Bi2Te5 and its Mn-doped counterparts. The application of pressure induces a SC in Ge2Bi2Te5, which shows a dome-shape phase diagram with the maximum Tc of 7.6 K at 23 GPa. Doping Mn into Ge2Bi2Te5 introduces an antiferromagnetic order at ambient pressure and strongly weakens the pressure-induced SC, demonstrating that magnetism and SC compete in this material system. Present study provides a new platform for investigating the interplay among band topology, magnetism, and SC.

cond-mat.supr-con↗

arXiv2026

Three-dimensional topological insulator feature of ternary chalcogenide Ge2Bi2Te5

The exploration of novel topological insulators (TIs) beyond binary chalcogenides has been accelerated in pursuit of exotic quantum states and device applications. Here, the layered ternary chalcogenide Ge2Bi2Te5 is identified as a three-dimensional TI. The bulk electronic structure of Ge2Bi2Te5 features a hole-type Fermi surface at Fermi level EF, which dominates the transport properties. Moreover, an unoccupied topological surface state with a Dirac point located at 290 meV above EF has been observed. Theoretical calculations confirm a bulk bandgap and a nontrivial Z2 topological invariant (000;1). The present study demonstrates that the material family of layered tetradymite-like ternary compounds is an important platform to explore exotic topological phenomena.

cond-mat.str-el↗

arXiv2026

Cooperative concurrence of 4f and 3d flat bands in kagome heavy-fermion metal YbCr6Ge6

Flat-band (FB) systems originating from special lattice geometry like in kagome metals as well as localized orbitals in the materials such as heavy-fermion (HF) compounds have induced intensive interest due to their band topology and strong electron correlation effects, leading to emergent quantum states of matter. However, the question of how these two distinct FBs coexist and interact remains unsettled. Here, we report that YbCr6Ge6 hosting both Cr-kagome lattice and Yb-4f electrons exhibits HF behaviors and a robust antiferromagnetic ground state with transition temperature TN = 3 K, significantly higher than other similar kagome metals with Yb ions. Angle-resolved photoemission spectroscopy measurements reveal the coexistence of FBs originating from both Cr-kagome lattice and localized Yb-4f electrons near Fermi energy level EF. More importantly, the clear spectroscopic signatures of a hybridization of Yb-4f FB with kagome-lattice-derived conduction bands and the high density of states of Cr-kagome FB near EF provide the underlying microscopic mechanisms of HF behaviors and enhanced antiferromagnetism in YbCr6Ge6. Our findings demonstrate that the novel kagome HF metals can not only host the cooperative coexistence of two different types of FBs, but also provide a paradigm material platform to explore the exotic correlated topological quantum phenomena.

cond-mat.str-el↗

arXiv2026

Nematic-fluctuation-mediated superconductivity in CuxTiSe2

The interplay among electronic nematicity, charge density wave, and superconductivity in correlated electronic systems has induced extensive research interest. Here, we discover the existence of nematic fluctuations in TiSe2 single crystal and investigate its evolution with Cu intercalation. It is observed that the elastoresistivity coefficient mEg exhibits a divergent temperature dependence following a Curie-Weiss law at high temperature. Upon Cu intercalation, the characteristic temperature T* of nematic fluctuation is progressively suppressed and becomes near zero when the superconductivity is optimized. Further intercalation of Cu leads to the sign change of T* and the suppression of superconductivity. These results strongly indicate that nematic phase transition may play a vital role in enhancing superconductivity in CuxTiSe2. Therefore, CuxTiSe2 provides a unique material platform to explore the nematic-fluctuation-mediated superconductivity.

cond-mat.supr-con↗

arXiv2025

Extreme orbital ab-plane upper critical fields far beyond Pauli limit in 4Hb-Ta(S, Se)2 bulk crystals

Transition metal disulfides 4Hb-Ta(S, Se)2 with natural heterostructure of 1T- and 1H-Ta(S, Se)2 layers have became the focus of correlated materials their unique combinations of Mott physics and possible topological superconductivity. In this work, we study the upper critical fields mu0Hc2 of 4Hb-TaS2 and 4Hb-TaS1.99Se0.01 single crystals systematically. Transport measurements up to 35 T show that both of ab-plane and c-axis upper critical fields (mu0Hc2,ab and mu0Hc2,c) for 4Hb-TaS2 and 4Hb-TaS1.99Se0.01 exhibit a linear temperature dependent behavior down to 0.3 K, suggesting the three-dimensional superconductivity with dominant orbital depairing mechanism in bulk 4Hb-Ta(S, Se)2. However, the zero-temperature mu0Hc2,ab(0) for both crystals are far beyond the Pauli paramagnetic limit mu0HP. It could be explained by the effects of spin-momentum locking in 1H-Ta(S, Se)2 layers with local inversion symmetry broken and the relatively weak intersublattice interaction between 1H layers due to the existence of 1T layers.

cond-mat.supr-con↗

arXiv2025

Nearly-room-temperature ferromagnetism and tunable anomalous Hall effect in atomically thin Fe4CoGeTe2

Itinerant ferromagnetism at room temperature is a key ingredient for spin transport and manipulation. Here, we report the realization of nearly-room-temperature itinerant ferromagnetism in Co doped Fe5GeTe2 thin flakes. The ferromagnetic transition temperature TC (~ 323 K - 337 K) is almost unchanged when thickness is down to 12 nm and is still about 284 K at 2 nm (bilayer thickness). Theoretical calculations further indicate that the ferromagnetism persists in monolayer Fe4CoGeTe2. In addition to the robust ferromagnetism down to the ultrathin limit, Fe4CoGeTe2 exhibits an unusual temperature- and thickness-dependent intrinsic anomalous Hall effect. We propose that it could be ascribed to the dependence of band structure on thickness that changes the Berry curvature near the Fermi energy level subtly. The nearly-room-temperature ferromagnetism and tunable anomalous Hall effect in atomically thin Fe4CoGeTe2 provide opportunities to understand the exotic transport properties of two-dimensional van der Waals magnetic materials and explore their potential applications in spintronics.

cond-mat.mtrl-sci↗

arXiv2025

Superconductivity in kagome metal YRu3Si2 with strong electron correlations

We report the detailed physical properties of YRu3Si2 with the Ru kagome lattice at normal and superconducting states. The results of resistivity and magnetization show that YRu3Si2 is a type-II bulk superconductor with Tc ~ 3.0 K. The specific heat measurement further suggests that this superconductivity could originate from the weak or moderate electron-phonon coupling. On the other hand, both large Kadawaki-Woods ratio and Wilson ratio indicate that there is a strong electron correlation effect in this system, which may have a connection with the featured flat band of kagome lattice.

cond-mat.supr-con↗

arXiv2025

Highly Efficient Room-Temperature Nonvolatile Magnetic Switching by Current in Fe3GaTe2 Thin Flakes

Effectively tuning magnetic state by using current is essential for novel spintronic devices. Magnetic van der Waals (vdW) materials have shown superior properties for the applications of magnetic information storage based on the efficient spin torque effect. However, for most of known vdW ferromagnets, the ferromagnetic transition temperatures lower than room temperature strongly impede their applications and the room-temperature vdW spintronic device with low energy consumption is still a long-sought goal. Here, we realize the highly efficient room-temperature nonvolatile magnetic switching by current in a single-material device based on vdW ferromagnet Fe3GaTe2. Moreover, the switching current density and power dissipation are about 300 and 60000 times smaller than conventional spin-orbit-torque devices of magnet/heavy-metal heterostructures. These findings make an important progress on the applications of magnetic vdW materials in the fields of spintronics and magnetic information storage.

cond-mat.mtrl-sci↗

arXiv2025

High Pressure Growth of Transition-Metal Monosilicide RhGe Single Crystals

Transition-metal monosilicide RhGe has been reported to exhibit weak itinerant ferromagnetism, superconductivity, and topological properties. In this study, we report the high-pressure growth of high-quality RhGe single crystals up to millimeter size using flux method. Transport measurements reveal the metallic behavior of RhGe between 2-300 K with Fermi liquid behavior at low temperature region. However, no superconductivity was observed with variations in Ge composition. Magnetic characterizations indicate that RhGe exhibits a paramagnetic behavior between 2-300 K. The high-quality, large-size RhGe single crystals pave the way for further investigation of their topological properties using spectroscopic techniques.

cond-mat.str-el↗

arXiv2025

Observation of topological Anderson Chern insulator phase in MnBi$_4$Te$_7$ monolayer

The correlation of topology and disorder has attracted great intention due to appropriate disorder could induce the phase transition between trivial and nontrivial topological states. While it is widely recognized that strong disorder can produce rich phase diagrams in topological nontrivial states, moderate disorder has been proposed to induce transitions into topologically nontrivial phases counter-intuitively, leading to the concept of topological Anderson insulators. This phenomenon has been theoretically explored and simulated in various systems, yet experimental realization in solid state systems has remained elusive due to challenges in controlling disorder. Here, we report the experimental observation of Chern insulator state signed by the coexistence of quantized Hall plateau and zero longitudinal resistance in monolayer MnBi$_4$Te$_7$ Hall bar device, which originally hosts a trivial insulating state with Chern number $C$ = 0 in clean limit. We demonstrate that the observed trivial to nontrivial transition in this monolayer device can be attributed to disorder, evidenced by universal conductance fluctuations. Our findings substantiate the existence of a long-sought topological Anderson Chern insulator in real materials, a unique variant of the topological Anderson insulator characterized by broken time-reversal-symmetry.

cond-mat.mes-hall↗

arXiv2024

Interstitial anionic electrons involved superconductivity and T-linear resistivity behavior in electride La3In

Electrides are unique materials because of the existence of interstitial anionic electrons (IAEs). Due to these loosely bound IAEs and their strong interaction with the framework of cations, electrides can host superconductivity with rather high Tc, especially under high pressure, as predicted in theory. However, the experimental observations of superconductivity in electrides are very rare, let alone the detailed studies on intrinsic properties of single crystals. Here, we report the superconducting and normal-state properties of electride La3In single crystals. La3In shows a type-II superconductivity with Tc ~ 9.4 K and a T-linear resistivity in a wide temperature range. Experimental measurements and theoretical calculations suggest that the relatively high Tc could be ascribed to the high density of states around the Fermi level caused by short flat bands along R-M direction and the strong electron-phonon coupling, partially derived from the IAEs. Meanwhile, the T-linear resistivity may reflect the significant electronic correlation effect in this material. These findings will shed light on understanding the role of IAEs in superconductivity and open a promising way to explore high-temperature superconductors in electrides.

cond-mat.supr-con↗

arXiv2024

Emergence of electric-field-tunable interfacial ferromagnetism in 2D antiferromagnet heterostructures

Van der Waals (vdW) magnet heterostructures have emerged as new platforms to explore exotic magnetic orders and quantum phenomena. Here, we study heterostructures of layered antiferromagnets, CrI3 and CrCl3, with perpendicular and in-plane magnetic anisotropy, respectively. Using magneto-optical Kerr effect microscopy, we demonstrate out-of-plane magnetic order in the CrCl3 layer proximal to CrI3, with ferromagnetic interfacial coupling between the two. Such an interlayer exchange field leads to higher critical temperature than that of either CrI3 or CrCl3 alone. We further demonstrate significant electric-field control of the coercivity, attributed to the naturally broken structural inversion symmetry of the heterostructure allowing unprecedented direct coupling between electric field and interfacial magnetism. These findings illustrate the opportunity to explore exotic magnetic phases and engineer spintronic devices in vdW heterostructures.

cond-mat.mtrl-sci↗

arXiv2024

Macroscopic Tunneling Probe of Moiré Spin Textures in Twisted CrI$_3$

Various noncollinear spin textures and magnetic phases have been predicted in twisted two-dimensional CrI$_3$ due to competing ferromagnetic (FM) and antiferromagnetic (AFM) interlayer exchange from moiré stacking - with potential spintronic applications even when the underlying material possesses a negligible Dzyaloshinskii-Moriya or dipole-dipole interaction. Recent measurements have shown evidence of coexisting FM and AFM layer order in small-twist-angle CrI$_3$ bilayers and double bilayers. Yet, the nature of the magnetic textures remains unresolved and possibilities for their manipulation and electrical readout are unexplored. Here, we use tunneling magnetoresistance to investigate the collective spin states of twisted double-bilayer CrI$_3$ under both out-of-plane and in-plane magnetic fields together with detailed micromagnetic simulations of domain dynamics based on magnetic circular dichroism. Our results capture hysteretic and anisotropic field evolutions of the magnetic states and we further uncover two distinct non-volatile spin textures (out-of-plane and in-plane domains) at $\approx$ 1° twist angle, with a different global tunneling resistance that can be switched by magnetic field.

cond-mat.mtrl-sci↗

arXiv2023

Revealing intrinsic domains and fluctuations of moiré magnetism by a wide-field quantum microscope

Moiré magnetism featured by stacking engineered atomic registry and lattice interactions has recently emerged as an appealing quantum state of matter at the forefront condensed matter physics research. Nanoscale imaging of moiré magnets is highly desirable and serves as a prerequisite to investigate a broad range of intriguing physics underlying the interplay between topology, electronic correlations, and unconventional nanomagnetism. Here we report spin defect-based wide-field imaging of magnetic domains and spin fluctuations in twisted double trilayer (tDT) chromium triiodide CrI3. We explicitly show that intrinsic moiré domains of opposite magnetizations appear over arrays of moiré supercells in low-twist-angle tDT CrI3. In contrast, spin fluctuations measured in tDT CrI3 manifest little spatial variations on the same mesoscopic length scale due to the dominant driving force of intralayer exchange interaction. Our results enrich the current understanding of exotic magnetic phases sustained by moiré magnetism and highlight the opportunities provided by quantum spin sensors in probing microscopic spin related phenomena on two-dimensional flatland.

cond-mat.mes-hall↗

arXiv2023

Pressure-tunable magnetic topological phases in magnetic topological insulator MnSb4Te7

Magnetic topological insulators, possessing both magnetic order and topological electronic structure, provides an excellent platform to research unusual physical properties. Here, we report a high-pressure study on the anomalous Hall effect of magnetic TI MnSb4Te7 through transports measurements combined with first-principle theoretical calculations. We discover that the ground state of MnSb4Te7 experiences a magnetic phase transition from the A-type antiferromagnetic state to ferromagnetic dominating state at 3.78 GPa, although its crystal sustains a rhombohedral phase under high pressures up to 8 GPa. The anomalous Hall conductance σxyA keeps around 10 Ω-1 cm-1, dominated by the intrinsic mechanism even after the magnetic phase transition. The results shed light on the intriguing magnetism in MnSb4Te7 and pave the way for further studies of the relationship between topology and magnetism in topological materials.

cond-mat.supr-con↗

arXiv2022

Ferromagnetic-antiferromagnetic coexisting ground states and exchange bias effects in $\bf{MnBi_4Te_7}$ and $\bf{MnBi_6Te_{10}}$

Natural superlattice structures $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2,...), in which magnetic $\rm{MnBi_2Te_4}$ layers are separated by nonmagnetic $\rm{Bi_2Te_3}$ layers, hold band topology, magnetism and reduced interlayer coupling, providing a promising platform for the realization of exotic topological quantum states. However, their magnetism in the two-dimensional limit, which is crucial for further exploration of quantum phenomena, remains elusive. Here, complex ferromagnetic (FM)-antiferromagnetic (AFM) coexisting ground states that persist up to the 2-septuple layers (SLs) limit are observed and comprehensively investigated in $\rm{MnBi_4Te_7}$ ($n$ = 1) and $\rm{MnBi_6Te_{10}}$ ($n$ = 2). The ubiquitous Mn-Bi site mixing modifies or even changes the sign of the subtle inter-SL magnetic interactions, yielding a spatially inhomogeneous interlayer coupling. Further, a tunable exchange bias effect is observed in $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2), arising from the coupling between the FM and AFM components in the ground state. Our work highlights a new approach toward the fine-tuning of magnetism and paves the way for further study of quantum phenomena in $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2,...) as well as their magnetic applications.

cond-mat.mtrl-sci↗

arXiv2022

Evidence of Noncollinear Spin Texture in Magnetic Moiré Superlattices

Moiré magnetism, parallel with moiré electronics that has led to novel correlated and topological electronic states, emerges as a new venue to design and control exotic magnetic phases in twisted magnetic two-dimensional(2D) crystals. Here, we report direct evidence of noncollinear spin texture in 2D twisted double bilayer (tDB) magnet chromium triiodide (CrI$_3$). Using magneto-optical spectroscopy in tDB CrI$_3$, we revealed the presence of a net magnetization, unexpected from the composing antiferromagnetic bilayers with compensated magnetizations, and the emergence of noncollinear spins, originated from the moiré exchange coupling-induced spin frustrations. Exploring the twist angle dependence, we demonstrated that both features are present in tDB CrI$_3$ with twist angles from 0.5$^o$ to 5$^o$, but are most prominent in the 1.1$^o$ tDB CrI$_3$. Focusing on the temperature dependence of the 1.1$^o$ tDB CrI$_3$, we resolved the dramatic suppression in the net magnetization onset temperature and the significant softening of noncollinear spins, as a result of the moiré induced frustration. Our results demonstrate the power of moiré superlattices in introducing novel magnetic phenomena that are absent in natural 2D magnets.

cond-mat.mtrl-sci↗