Doctor of Philosophy, Chinese Academy Of Sciences (2018)
Observation of two types of charge-density-wave orders in superconducting La2-xSrxCuO4.
2019; 10 (1): 3269
The discovery of charge- and spin-density-wave (CDW/SDW) orders in superconducting cuprates has altered our perspective on the nature of high-temperature superconductivity (SC). However, it has proven difficult to fully elucidate the relationship between the density wave orders and SC. Here, using resonant soft X-ray scattering, we study the archetypal cuprate La2-xSrxCuO4 (LSCO) over a broad doping range. We reveal the existence of two types of CDW orders in LSCO, namely CDW stripe order and CDW short-range order (SRO). While the CDW-SRO is suppressed by SC, it is partially transformed into the CDW stripe order with developing SDW stripe order near the superconducting Tc. These findings indicate that the stripe orders and SC are inhomogeneously distributed in the superconducting CuO2 planes of LSCO. This further suggests a new perspective on the putative pair-density-wave order that coexists with SC, SDW, and CDW orders.
View details for DOI 10.1038/s41467-019-11167-z
View details for PubMedID 31332190
Ultrasensitive Mid-wavelength Infrared Photodetection Based on a Single InAs Nanowire
2019; 13 (3): 3492–99
One-dimensional InAs nanowire (NW)-based photodetectors have been widely studied due to their potential application in mid-wavelength infrared (MWIR) photon detection. However, the limited performance and complicated photoresponse mechanism of InAs NW-based photodetectors have held back their true potential for real application. In this study, we developed ferroelectric polymer P(VDF-TrFE)-coated InAs NW-based photodetectors and demonstrated that the electrostatic field caused by polarized ferroelectric materials modifies the surface electron-hole distribution as well as the band structure of InAs NWs, resulting in ultrasensitive photoresponse and a wide photodetection spectral range. Our single InAs NW photodetectors exhibit a high responsivity ( R) of 1.6 × 104 A W-1 as well as a corresponding detectivity ( D*) of 1.4 × 1012 cm·Hz1/2 W-1 at a light wavelength of 3.5 μm without an applied gate voltage, ∼3-4 orders higher than the maximum value of photoresponsivity reported or commercially used MWIR photodetectors. Moreover, our device shows below band gap photoresponse for 4.3 μm MWIR light with R of 9.6 × 102 A W-1 as well as a corresponding D* of ∼8.5 × 1010 cm·Hz1/2 W-1 at 77 K. Our study shows that this approach is promising for fabrication of high-performance NW-based photodetectors for MWIR photon detection.
View details for DOI 10.1021/acsnano.8b09649
View details for Web of Science ID 000462950500075
View details for PubMedID 30817125
- Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa2CU3O6.73 PHYSICAL REVIEW B 2018; 97 (17)
Surface-to-Bulk Redox Coupling through Thermally Driven Li Redistribution in Li- and Mn-Rich Layered Cathode Materials.
Journal of the American Chemical Society
Li- and Mn-rich (LMR) layered cathode materials have demonstrated impressive capacity and specific energy density thanks to their intertwined redox centers including transition metal cations and oxygen anions. Although tremendous efforts have been devoted to the investigation of the electrochemically driven redox evolution in LMR cathode at ambient temperature, their behavior under a mildly elevated temperature (up to ∼100 °C), with or without electrochemical driving force, remains largely unexplored. Here we show a systematic study of the thermally driven surface-to-bulk redox coupling effect in charged Li1.2Ni0.15Co0.1Mn0.55O2. We for the first time observed a charge transfer between the bulk oxygen anions and the surface transition metal cations under ∼100 °C, which is attributed to the thermally driven redistribution of Li ions. This finding highlights the nonequilibrium state and dynamic nature of the LMR material at deeply delithiated state upon a mild temperature perturbation.
View details for DOI 10.1021/jacs.9b05349
View details for PubMedID 31287957
- Understanding spin configuration in the geometrically frustrated magnet TbB4: A resonant soft X-ray scattering study CURRENT APPLIED PHYSICS 2018; 18 (11): 1205–11
- Persistent low-energy phonon broadening near the charge-order q vector in the bilayer cuprate Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW B 2018; 98 (3)
- Coincident onset of charge-density-wave order at a quantum critical point in underdoped YBa2Cu3Ox PHYSICAL REVIEW B 2018; 97 (22)
Mesoscale Battery Science: The Behavior of Electrode Particles Caught on a Multispectral X-ray Camera.
Accounts of chemical research
Functional materials and devices are usually morphologically complex and chemically heterogeneous. Their structures are often designed to be hierarchical because of the desired functionalities, which usually require many different components to work together in a coherent manner. The lithium ion battery, as an energy storage device, is a very typical example of this kind of structure. In a lithium ion battery, the cathode, anode, and separator are soaked in a liquid electrolyte, facilitating the back and forward shuttling of the lithium ions for energy storage and release. The desired performance of a lithium ion battery has many different aspects that need to be engineered and balanced depending on the targeted applications. In most cases, the cathode material has become the limiting factor for further improvements and, thus, has attracted intense attention from the research community. While the improvement in the overall performance of the lithium ion battery is the ultimate goal of the research in this field, understanding the relationship between the microscopic properties and the macroscopic behaviors of the materials/devices can inform the design of better battery chemistries for practical applications. As a result, it is of great fundamental and practical importance to investigate the electrode materials using experimental probes that can provide good chemical sensitivity and sufficient spatial resolution, ideally, under operating conditions. With this motivation, our group has been focusing on the development of the nanoscale full-field X-ray spectro-microscopy, which has now become a well-recognized tool for imaging battery electrode materials at the particle level. With nanoscale spatial resolution, this technique can effectively and efficiently tackle the intrinsically complicated mesoscale chemistry. It allows us to monitor the particles' morphological and chemical evolution upon battery operation, providing valuable insights that can be incorporated into the design of new battery chemistries. In this Account, we review a series of our recent studies of battery electrode materials using nanoscale full-field X-ray spectro-microscopy. The materials that are the subjects of our studies, including layer-structured and spinel-structured oxide cathodes, are technically very important as they not only play an important role in today's devices but also possess promising potential for future developments. We discuss how the subparticle level compositional and state-of-charge heterogeneity can be visualized and linked to the bulk performance through systematic quantification of the imaging data. Subsequently, we highlight recent ex situ and in situ observations of the cathode particles' response to different reaction conditions, including the spontaneously adjusted reaction pathways and the morphological changes for the mechanical strain release. The important role of surface chemistry in the system is also discussed. While the microscopic investigation at the particle level provides useful insights, the degree to which this represents the overall properties of the battery is always a question for further generalizing the conclusions. In order to address this concern, we finally discuss a high throughput experimental approach, in which a large number of cathode particles are scanned. We discuss a case study that demonstrates the identification and analysis of functionally important minority phases in an operating battery cell through big data mining methods. With an emphasis on the data/information mining aspect of the nanoscale X-ray spectro-microscopic study of battery cathode particles, we anticipate that this Account will attract more research to this field.
View details for DOI 10.1021/acs.accounts.8b00123
View details for PubMedID 29889493