The emergence of giant multicaloric phenomena near room temperature
Tapas Samanta, Pol Lloveras, Ahmad Us Saleheen, Daniel L. Lepkowski, Emily Kramer, Igor Dubenko, Philip W. Adams, David P. Young, Maria Barrio, Josep Ll. Tamari… 展开作者
Tapas Samanta, Pol Lloveras, Ahmad Us Saleheen, Daniel L. Lepkowski, Emily Kramer, Igor Dubenko, Philip W. Adams, David P. Young, Maria Barrio, Josep Ll. Tamarit, Naushad Ali, Shane Stadler
Caloric responses (temperature changes) can be induced in solid-state materials by applying external stimuli such as stress, pressure, and electric and magnetic fields. The magnetic-field-stimulated response is called the magnetocaloric effect, and materials that exhibit this property have long been sought for applications in room temperature magnetic cooling due to their potentially superior efficiency and low impact on the environment. Other solid-state caloric phenomena are less developed, but are likewise under intense investigation. Here we introduce a new material that not only displays giant barocaloric (hydrostatic-pressure-induced) properties, but also a large magnetocaloric response near room temperature. It is unprecedented that two caloric effects of such extreme magnitude occur in the same material and at the same temperature. These effects originate from a magnetostructural transition and a magneto-volume (magnetostriction) effect where the volume change is large enough to force the system from a localized ordered state into an itinerant paramagnetic state.
The existence and feasibility of the multicaloric, polycrystalline material 0.8Pb(Fe1/2Nb1/2)O3-0.2Pb(Mg1/2W1/2)O3, exhibiting magnetocaloric and electrocaloric properties, are demonstrated. Both the electrocaloric and magnetocaloric effects are observed over a broad temperature range below room temperature. The maximum magnetocaloric temperature change of ~0.26 K is obtained with a magnetic-field amplitude of 70 kOe at a temperature of 5 K, while the maximum electrocaloric temperature change of ~0.25 K is obtained with an electric-field amplitude of 60 kV/cm at a temperature of 180 K. The mat…
Two-dimensional (2D) multiferroics are key candidate materials towards advancement of smart technology. Here, we employed a simple synthesis approach to address the long-awaited dream of developing ferroelectric and multiferroic 2D materials, specially in the new class of materials called MXenes. The etched Ti$_3$C$_2$T$_x$ MXene was first synthesized after HF-treatment followed by delamination process for successful synthesis of free-standing Ti$_3$C$_2$T$_x$ film. The free-standing film was then exposed to air at room-temperature as well as heated at different temperature to form TiO$_2$ lay…
We report emergence of photoluminescence at room temperature in trigonal $Cs_3Bi_2Br_9$ at high pressures. Enhancement in intensity with pressure is found to be driven by increase in distortion of $BiBr_6$ octahedra and iso-structural transitions. Electronic band structure calculations show the sample in the high pressure phase to be an indirect band gap semiconductor. The luminescence peak profile show signatures related to the recombination of free and self trapped excitons, respectively. Blue shift of the both peaks till about 4.4 GPa are due to the exciton recombination before relaxation d…
Strong correlations between electrons and holes can drive the existence of an electron-hole liquid (EHL) state, typically at high carrier densities and low temperatures. The recent emergence of quasi-2D monolayer transition metal dichalcogenides (TMDCs) provide ideal systems to explore the EHL state since ineffective screening of the out of plane field lines in these quasi-2D systems allows for stronger charge carrier correlations in contrast to conventional 3D bulk semiconductors and enabling the existence of the EHL at high temperatures. Here we construct the phase diagram for the photo-indu…
Recently, much interest has emerged in fluid-like electric charge transport in various solid-state systems. The hydrodynamic behavior of the electronic fluid reveals itself as a decrease of the electrical resistance with increasing temperature (the Gurzhi effect) in narrow conducting channels, polynomial scaling of the resistance as a function of the channel width, substantial violation of the Wiedemann-Franz law supported by the emergence of the Poiseuille flow. Similarly to whirlpools in flowing water, the viscous electronic flow generates vortices, resulting in abnormal sign-changing electr…
Engineering non-linear hybrid light-matter states in tailored optical lattices is a central research strategy for the simulation of complex Hamiltonians. Excitons in atomically thin crystals are an ideal active medium for such purposes, since they couple strongly with light and bear the potential to harness giant non-linearities and interactions while presenting a simple sample-processing and room temperature operability. We demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS$_{2}$ monolayer. We …
The emergence of halide perovskites in photovoltaics has diversified the research on this material family and extended their application towards several fields in the optoelectronics, such as photo- and ionizing-radiation-detectors. One of the most basic characterization protocols consist on measuring the dark current-voltage (J-V) curve of symmetrically contacted samples for identifying the different regimes of space-charge-limited current (SCLC). Customarily, J=C*V^n curves indicate the Mott-Gurney law when n=2, or the Child-Langmuir ballistic regime of SCLC when n=3/2. The latter can be oft…
Altermagnetism and Room-Temperature Metal-to-Insulator Transition in CsCr$_2$S$_2$O
Zhejiang University of Technology（浙江工业大学）；Zhejiang University（浙江大学）；Hangzhou Normal University（杭州师范大学）；Chinese Academy of Engineering Physics（中国工程物理研究院）；Bruker Scientific Instruments Co., Ltd（布鲁克科学仪器有限公司）；Zhejiang Laboratory（浙江实验室）；Nanjing University（南京大学）
Room-temperature multistage metastability in a moiré superstructure
Tsung-Dao Lee Institute, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交大李政道理论与计算科学中心，物理与天文学院）；Massachusetts Institute of Technology（麻省理工学院）；Stanford University（斯坦福大学）；Peking University（北京大学）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Tianjin University of Technology（天津理工大学）
Helimagnetic materials are identified as promising for novel spintronic applications. Since helical spin order is manifested as a compromise of competing magnetic exchange interactions, its emergence is limited by unique constraints imposed by the crystalline lattice and the interaction geometries, as exemplified by the multiferroic perovskite manganites with large orthorhombic distortion. Here we show that a simple cubic perovskite SrCoO$_3$ with room-temperature ferromagnetism has the potential to host helimagnetic order upon isotropic lattice expansion. Increasing the Ba content $x$ in Sr$_…
Quantum information science and engineering requires novel low-loss magnetic materials for magnon-based quantum-coherent operations. The search for low-loss magnetic materials, traditionally driven by applications in microwave electronics near room-temperature, has gained additional constraints from the need to operate at cryogenic temperatures for many applications in quantum information science and technology. Whereas yttrium iron garnet (YIG) has been the material of choice for decades, the emergence of molecule-based materials with robust magnetism and ultra-low damping has opened new aven…
Optical evidence of surface state suppression in Bi based topological insulators
凝聚态研究的一个关键挑战是拓扑绝缘体（TI）化合物的优化，以研究其独特的表面状态和未来的应用。真正绝缘的体态将允许利用预测的表面态性质，如防止反向散射，无耗散的自旋极化电流，以及新粒子的出现。为此，最近取得了重大进展，引入了高电阻的Bi $_2$ Te $_2$ Se，其中在低温下观察到表面态电导和量子振荡。然而，一个悬而未决的关键问题仍然存在：虽然室温ARPES研究揭示了TI表面状态的明确证据，但它们在运输实验中的观察仅限于低温。更好地理解这种表面态抑制在高温下是根本的利益，并推动设备应用的边界向室温操作至关重要。在这项工作中，我们同时测量TI体和表面状态，通过温度相关的光学光谱，结合运输和ARPES测量。我们发现在低温下相干表面态输运的证据，并提出声子介导的体和表面态之间的耦合抑制表面电导随着温度的升高。
Magnetic Weyl semimetals (mWSMs) are characterized by linearly dispersive bands with chiral Weyl node pairs associated with broken time reversal symmetry. One of the hallmarks of mWSMs is the emergence of large intrinsic anomalous Hall effect. On heating the mWSM above its Curie temperature, the magnetism vanishes while exchange-split Weyl point pairs collapse into doubly-degenerated gapped Dirac states. Here, we reveal the attractive potential of these Dirac nodes in paramagnetic state for efficient spin current generation at room temperature via the spin Hall effect. Ni and In are introduced…
In-Situ TEM Observation of Solid-State Phase Evolution in High-Entropy Alloy Nanoparticles
University of Petroleum and Energy Studies (UPES)（石油与能源大学）；Indian Institute of Technology, Kharagpur（印度理工学院哈格普尔分校）；Brazilian Centre for Research in Energy and Materials（巴西能源与材料研究中心）；State University of Campinas（坎皮纳斯州立大学）；Rice University（莱斯大学）；Federal University of ABC (UFABC)（ABC联邦大学）；Michigan Technological University（密歇根理工大学）
X-ray characterisation methods have undoubtedly enabled cutting-edge advances in all aspects of materials research. Despite the enormous breadth of information that can be extracted from these techniques, the challenge of radiation-induced sample change and damage remains prevalent. This is largely due to the emergence of modern, high-intensity X-ray source technologies and growing potential to carry out more complex, longer duration in-situ or in-operando studies. The tunability of synchrotron beamlines enables the routine application of photon energy-dependent experiments. This work explores…
Spontaneous Enhancement of Dzyaloshinskii-Moriya Interaction via Field-Cooling-Induced Interface Engineering in 2D van der Waals Ferromagnetic ternary Tellurides
Wuhan University（武汉大学）；Southeast University（东南大学）；Yanshan University（燕山大学）；Beihang University（北京航空航天大学）；Wuhan Institute of Quantum Technology（武汉量子技术研究院）
X-ray diffraction pressure studies at room temperature demonstrate that the spinel FeAl$_{2}$O$_{4}$ transforms to a tetragonal phase at ~18 GPa. This tetragonal phase has a highly irregular unit-cell volume versus pressure dependence up to ~45 GPa, after which a transformation to a Cmcm post-spinel phase is onset. This is attributable to pressure driven Fe-Al site inversion at room temperature, corroborated by signatures in the 57Fe Mössbauer spectroscopy pressure data. At the tetragonal to post-spinel transition, onset in the range 45-50 GPa, there is a concurrent emergence of a non-magnetic…
Although ferromagnets are found in all kinds of technological applications, only few substances are known to be intrinsically ferromagnetic at room temperature. In the past twenty years, a plethora of new artificial ferromagnetic materials have been found by introducing defects into non-magnetic host materials. In contrast to the intrinsic ferromagnetic materials, they offer an outstanding degree of material engineering freedom, provided one finds a type of defect to functionalize every possible host material to add magnetism to its intrinsic properties. Still, one controversial question remai…
Controllable geometric manipulation via micromachining techniques provides a promising tool for enhancing useful topological electrical responses relevant to future applications such as quantum information science. Here we present microdevices fabricated with focused ion beam from indium-doped topological insulator Pb1-xSnxTe. With device thickness on the order of 1 μm and an extremely large bulk resistivity, we achieve an unprecedented enhancement of the surface contribution to about 30% of the total conductance near room temperature. The surface contribution increases as the temperature is r…
Nonreciprocity and nonreciprocal optical devices play a vital role in modern photonic technologies by enforcing one-way propagation of light. Most nonreciprocal devices today are made from a special class of low-loss ferrites that exhibit a magneto-optical response in the presence of an external static magnetic field. While breaking transmission symmetry, ferrites fail to satisfy the need for miniaturization of photonic circuitry due to weak character of nonreciprocal responses at optical wavelengths and are not easy to integrate into on-chip photonic systems. These challenges led to the emerg…
