| 1. |
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| 2. |
- Syndikus, I., et al.
(author)
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Probing the Z = 6 spin-orbit shell gap with (p,2p) quasi-free scattering reactions
- 2020
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 809
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Journal article (peer-reviewed)abstract
- The evolution of the traditional nuclear magic numbers away from the valley of stability is an active field of research. Experimental efforts focus on providing key spectroscopic information that will shed light into the structure of exotic nuclei and understanding the driving mechanism behind the shell evolution. In this work, we investigate the Z=6 spin-orbit shell gap towards the neutron dripline. To do so, we employed NA(p,2p)CA−1 quasi-free scattering reactions to measure the proton component of the 21+ state of 16,18,20C. The experimental findings support the notion of a moderate reduction of the proton 1p1/2−1p3/2 spin-orbit splitting, at variance to recent claims for a prevalent Z=6 magic number towards the neutron dripline.
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| 3. |
- Thota, S., et al.
(author)
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Unraveling the nature of ferrimagnetism and associated exchange interactions in distorted honeycomb Ni4Nb2O9
- 2022
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 106:13
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Journal article (peer-reviewed)abstract
- Ferrimagnetism in orthorhombic Ni4Nb2O9 below its Neel temperature, T-FN similar to 76K is reported to result from two inequivalent Ni2+ ions having different magnetic moments. However, a clear understanding of the temperature variation of its magnetization [M(T)] for T > T-FN and T < T-FN in terms of a single set of exchange parameters is still lacking. In this work, experimental results obtained from a detailed analysis of the temperature and magnetic field dependence of magnetization [M(T, H)], ac-magnetic susceptibility [chi(ac)( f, T, H)], and heat-capacity [C-P(T, H)] measurements are combined with theoretical analysis to provide new insights into the nature of ferrimagnetism in Ni4Nb2O9. X-ray diffraction/Rietveld analysis of the prepared sample yielded the structural parameters of the orthorhombic crystal in agreement with previous studies, whereas x-ray photoelectron spectroscopy confirmed the Ni2+ and Nb5+ electronic states in Ni4Nb2O9. Analysis of chi(ac)(T) shows the paramagnetic-to-ferrimagnetic transition occurs at 76.5 K (T-FN), which increases with applied field H as T-FN proportional to H-0.35 due to the coupling of the ferromagnetic component with H. For T > T-FN, the chi(dc) versus T data are fitted to the Neel's expression for ferrimagnets, yielding the g-factors for the two Ni2+ ions as g(A) = 2.47 and g(B) = 2.10. Also, the antiferromagnetic molecular field constants between the A and B sublattices were evaluated as N-AA = 26.31, N-BB = 8.59, and N-AB = 43.06, which, in turn, yield the antiferromagnetic exchange parameters: J(AA)/k(B) = 4.27 K, J(BB)/k(B) = 1.40 K, and J(AB)/k(B) = 6.98 K. For T < T-FN, the M versus T data clearly show the magnetic compensation point at T-COM similar to 33 K. The mathematical model presented here using the magnitudes of NAA, NBB, and NAB correctly predicts the position of T-COM as well the temperature variation of M both above and below T-COM. The data of C-P(T) versus T shows a lambda-type anomaly across T-FN. After subtracting the lattice contribution, the C-P(T) data are fitted to C-P = A(T - T-N)((-alpha)) yielding the critical exponent alpha = 0.14(0.12) for T < T-FN (T > T-FN), which is a characteristic of second-order phase transition. Magnetic entropy changes determined from the M-H isotherms shows that the applied field H enhances the magnetic ordering for T > T-FN and T < T-COM, but for T-COM < T < T-FN, the spin disorder increases with the increase in H. The temperature variation of the measured coercivity H-C(T) and remanence M-R(T) from 1.9 K to T-FN initially show a decreasing trend, becoming zero at T-COM, then followed by an increase and eventually becoming zero again at T-FN.
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| 4. |
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| 5. |
- Singh, S, et al.
(author)
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Nanotechnology Facilitated Cultured Neuronal Network and Its Applications
- 2021
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In: International journal of molecular sciences. - : MDPI AG. - 1422-0067. ; 22:11
-
Journal article (peer-reviewed)abstract
- The development of a biomimetic neuronal network from neural cells is a big challenge for researchers. Recent advances in nanotechnology, on the other hand, have enabled unprecedented tools and techniques for guiding and directing neural stem cell proliferation and differentiation in vitro to construct an in vivo-like neuronal network. Nanotechnology allows control over neural stem cells by means of scaffolds that guide neurons to reform synaptic networks in suitable directions in 3D architecture, surface modification/nanopatterning to decide cell fate and stimulate/record signals from neurons to find out the relationships between neuronal circuit connectivity and their pathophysiological functions. Overall, nanotechnology-mediated methods facilitate precise physiochemical controls essential to develop tools appropriate for applications in neuroscience. This review emphasizes the newest applications of nanotechnology for examining central nervous system (CNS) roles and, therefore, provides an insight into how these technologies can be tested in vitro before being used in preclinical and clinical research and their potential role in regenerative medicine and tissue engineering.
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| 6. |
- Singha, A. D., et al.
(author)
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Reentrant canonical spin-glass dynamics and tunable field-induced transitions in (GeMn)Co2O4 Kagomé lattice
- 2024
-
In: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 36:7
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Journal article (peer-reviewed)abstract
- We report on the reentrant canonical semi spin-glass characteristics and controllable field-induced transitions in distorted Kagomé symmetry of (GeMn)Co2O4. This B-site spinel exhibits complicated, yet interesting magnetic behaviour in which the longitudinal ferrimagnetic (FiM) order sets in below the Néel temperature TFN ∼ 77 K due to uneven moments of divalent Co (↑ 5.33 μB) and tetravalent Mn (↓ 3.87 μB) which coexists with transverse spin-glass state below 72.85 K. Such complicated magnetic behaviour is suggested to result from the competing anisotropic superexchange interactions (JAB/kB ∼ 4.3 K, JAA/kB ∼ −6.2 K and JBB/kB ∼ −3.3 K) between the cations, which is extracted following the Néel's expression for the two-sublattice model of FiM. Dynamical susceptibility (χac (f, T)) and relaxation of thermoremanent magnetization, MTRM (t) data have been analysed by means of the empirical scaling-laws such as Vogel–Fulcher law and Power law of critical slowing down. Both of which reveal the reentrant spin-glass like character which evolves through a number of intermediate metastable states. The magnitude of Mydosh parameter (Ω ∼ 0.002), critical exponent zυ = (6.7 ± 0.07), spin relaxation time τ0 = (2.33 ± 0.1) × 10−18 s, activation energy Ea/kB = (69.8 ± 0.95) K and interparticle interaction strength (T0 = 71.6 K) provide the experimental evidences for canonical spin-glass state below the spin freezing temperature TF = 72.85 K. The field dependence of TF obtained from χac (T) follows the irreversibility in terms of de Almeida–Thouless mean-field instability in which the magnitude of crossover scaling exponent Φ turns out to be ∼2.9 for the (Ge0.8Mn0.2)Co2O4. Isothermal magnetization plots reveal two field-induced transitions across 9.52 kOe (HSF1) and 45.6 kOe (HSF2) associated with the FiM domains and spin-flip transition, respectively. Analysis of the inverse paramagnetic susceptibility after subtracting the temperature independent diamagnetic term (=−3 × 10−3 emu mol−1 Oe−1) results in the effective magnetic moment = 7.654 μB/f.u. This agrees well with the theoretically obtained = 7.58 μB/f.u. resulting the cation distribution in support of the Hund's ground state spin configuration and of Mn4+ and Co2+, respectively. The H–T phase diagram has been established by analysing all the parameters (TF(H), TFN(H), HSF1(T) and HSF2(T)) extracted from various magnetization measurements. This diagram enables clear differentiation among the different phases of the (GeMn)Co2O4 and also illustrates the demarcation between short-range and long-range ordered regions.
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| 7. |
- Pramanik, Prativa, et al.
(author)
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Interplay of lattice-spin-orbital coupling and Jahn-Teller effect in noncollinear spinel Ti x Mn1-x (Fe y Co1-y )2O4 : a neutron diffraction study
- 2024
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In: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 36:35
-
Journal article (peer-reviewed)abstract
- Local magnetostructural changes and dynamical spin fluctuations in doubly diluted spinel TixMn1-x(FeyCo1-y)(2)O-4 has been reported by means of neutron diffraction and magnetization studies. Two distinct sets of compositions (i) x(Ti) = 0.20 and y(Fe) = 0.18; (ii) x(Ti) = 0.40 and y(Fe) = 0.435 have been considered for this study. The first compound of equivalent stoichiometry Ti0.20Mn0.80Fe0.36Co1.64O4 exhibits enhanced tetragonal distortion across the ferrimagnetic transition temperature T-C = 258 K in comparison to the end compound MnCo2O4 (T-C similar to 180 K) with a characteristic ratio c(t)/root 2a(t) of 0.99795(8) demonstrating robust lattice-spin-orbital coupling. However, in the second case Ti0.40Mn0.60Fe0.87Co1.13O4 with higher B-site compositions, the presence of Jahn-Teller ions with distinct behavior appears to counterbalance the strong tetragonal distortion thereby ceasing the lattice-spin-orbital coupling. Both the investigated systems show the coexistence of noncollinear antiferromagnetic and ferrimagnetic components in cubic and tetragonal settings. On the other hand, the dynamical ac-susceptibility, chi(ac)(T) reveals a cluster spin-glass state with Gabay-Toulouse (GT) like mixed phases behaviour below T-C. Such dispersive behaviour appears to be sensitive to the level of octahedral substitution. Further, the field dependence of chi(ac)(T) follows the weak anisotropic GT-line behaviour with crossover exponent Phi lies in the range 1.38-1.52 on the H-T plane which is in contrast to the B-site Ti substituted MnCo2O4 spinel that appears to follow irreversible non-mean-field AT-line behaviour (Phi similar to 3 + delta). Finally, the Arrott plots analysis indicates the presence of a pseudo first-order like transition (T < 20 K) which is in consonance with and zero crossover of the magnetic entropy change within the frozen spin-glass regime.
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| 8. |
- Pramanik, P., et al.
(author)
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Neutron diffraction evidence for local spin canting, weak Jahn-Teller distortion, and magnetic compensation in Ti1-xMnxCo2O4 spinel
- 2020
-
In: Journal of Physics. - : IOP PUBLISHING LTD. - 0953-8984 .- 1361-648X. ; 32:24
-
Journal article (peer-reviewed)abstract
- A systematic study using neutron diffraction and magnetic susceptibility is reported on Mn substituted ferrimagnetic inverse spinel Ti1-xMnxCo2O4 in the temperature interval 1.6 K T 300 K. Our neutron diffraction study reveals cooperative distortions of the TO6 octahedra in the Ti1-xMnxCo2O4 system for all the Jahn-Teller active ions T = Mn3+ , Ti3+ and Co3+ , having the electronic configurations 3d(1), 3d(4) and 3d(6), respectively which are confirmed by the x-ray photoelectron spectroscopy. Two specific compositions (x = 0.2 and 0.4) have been chosen in this study because these two systems show unique features such as; (i) noncollinear Yafet-Kittel type magnetic ordering, and (ii) weak tetragonal distortion with c/a < 1, in which the apical bond length d(c)(T-B-O) is longer than the equatorial bond length d(ab)(T-B-O) due to the splitting of the e(g) level of Mn3+ ions into and . For the composition x = 0.4, the distortion in the TBO6 octahedra is stronger as compared to x = 0.2 because of the higher content of trivalent Mn. Ferrimagnetic ordering in Ti0.6Mn0.4Co2O4 and Ti0.8Mn0.2Co2O4 sets in at 110.3 and 78.2 K, respectively due to the presence of unequal magnetic moments of cations, where Ti3+ , Mn3+ , and Co3+ occupy the octahedral, whereas, Co2+ sits in the tetrahedral site. For both compounds an additional weak antiferromagnetic component could be observed lying perpendicular to the ferrimagnetic component. The analysis of static and dynamic magnetic susceptibilities combined with the heat-capacity data reveals a magnetic compensation phenomenon (MCP) at T-COMP = 25.4 K in Ti0.8Mn0.2Co2O4 and a reentrant spin-glass behaviour in Ti0.6Mn0.4Co2O4 with a freezing temperature of 110.1 K. The MCP in this compound is characterized by sign reversal of magnetization and bipolar exchange bias effect below T-COMP with its magnitude depending on the direction of external magnetic field and the cooling protocol.
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| 9. |
- Chowdhury, Mouli Roy, et al.
(author)
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Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO4
- 2022
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In: Journal of Physics. - : IOP Publishing Ltd. - 0953-8984 .- 1361-648X. ; 34:27
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Journal article (peer-reviewed)abstract
- The nature of magnetism in the doubly-diluted spinel ZnTiCoO4 = (Zn2+)( A ) [Ti4+Co2+]( B )O-4 is reported here employing the temperature and magnetic field (H) dependence of dc susceptibility (chi), ac susceptibilities (chi ' and chi ''), and heat capacity (C (p)) measurements. Whereas antiferromagnetic (AFM) Neel temperature T (N) = 13.9 K is determined from the peak in the partial differential (chi T)/ partial differential T vs T plot, the fit of the relaxation time tau (determined from the peak in the chi '' vs T data at different frequencies) to the Power law: tau = tau (0) [(T - T (SG))/T (SG)](-z nu ) yields the spin glass freezing temperature T (SG) = 12.9 K, z nu similar to 11.75, and tau (0) similar to 10(-12) s. Since the magnitudes of tau (0) and z nu depend on the magnitude of T (SG), a procedure is developed to find the optimum value of T (SG) = 12.9 K. A similar procedure is used to determine the optimum T (0) = 10.9 K in the Vogel-Fulcher law: tau = tau (0) exp[E (a)/k (B)(T - T (0))] yielding E (a)/k (B) = 95 K, and tau (0) = 1.6 x 10(-13) s. It is argued that the comparatively large magnitude of the Mydosh parameter omega = 0.026 and k (B) T (0)/E (a) = 0.115 (MUCH LESS-THAN1) suggests cluster spin-glass state in ZnTiCoO4 below T-SG. In the C (p) vs T data from 1.9 K to 50 K, only a broad peak near 20 K is observed. This and absence of lambda-type anomaly near T (N) or T (SG) combined with the reduced value of change in magnetic entropy from 50 K to 1.9 K suggests only short-range AFM ordering in the system, consistent with spin-glass state. The field dependence of T (SG) shows slight departure (phi similar to 4.0) from the non-mean-field Almeida-Thouless line T (SG)(H) = T (SG)(0) (1 - AH (2/phi )). Strong temperature dependence of magnetic viscosity S and coercivity H (C) without exchange bias, both tending to zero on approach to T (SG) from below, further support the spin-glass state which results from magnetic dilution driven by diamagnetic Zn2+ and Ti4+ ions leading to magnetic frustration. Magnetic phase diagram in the H-T plane is established using the high-field magnetization data M(H, T) for T < T (N) which reveals rapid decrease of T (SG) with increase in H whereas decrease in T (N) with increase in H is weaker, typical of AFM systems. For T > T (N), the data of chi vs T are fit to the modified Curie-Weiss law, chi = chi (0) + C/(T + theta), with chi (0) = 3.2 x 10(-4) emu mol(-1) Oe(-1) yielding theta = 4 K and C = 2.70 emu K mol(-1) Oe(-1). This magnitude of C yields effective magnetic moment = 4.65 mu (B) for Co2+, characteristic of Co2+ ions with some contribution from spin-orbit coupling. Molecular field theory with effective spin S = 3/2 of Co2+ is used to determine the nearest-neighbor exchange constant J (1)/k (B) = 2. 39 K AFM and next-nearest-neighbor exchange constant J (2)/k (B) = -0.66 K (ferromagnetic).
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| 10. |
- Ghosh, Sayandeep, et al.
(author)
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Antiferromagnetism, spin-glass state, H-T phase diagram, and inverse magnetocaloric effect in Co2RuO4
- 2020
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In: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 32:48
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Journal article (peer-reviewed)abstract
- Static and dynamic magnetic properties of normal spinel Co2RuO4= (Co2+)A[Co3+Ru3+](B)O-4 are reported based on our investigations of the temperature (T), magnetic field (H) and frequency (f) dependence of the ac-magnetic susceptibilities and dc-magnetization (M) covering the temperature rangeT= 2 K-400 K and H up to 90 kOe. These investigations show that Co2RuO4 exhibits an antiferromagnetic (AFM) transition at T-N similar to 15.2 K, along with a spin-glass state at slightly lower temperature (T-SG) near 14.2 K. It is argued thatT(N)is mainly governed by the ordering of the spins of Co2+ ions occupying theA-site, whereas the exchange interaction between the Co2+ ions on theA-site and randomly distributed Ru(3+)on theB-site triggers the spin-glass phase, Co3+ ions on theB-site being in the low-spin non-magnetic state. Analysis of measurements ofM(H,T) for TT-N, analysis of the paramagnetic susceptibility (chi) vs.Tdata are fit to the modified Curie-Weiss law,chi=chi(0)+C/(T+theta), with chi(0)= 0.0015 emu mol(-1)Oe(-1)yielding theta= 53 K andC= 2.16 emu-K mol(-1)Oe(-1), the later yielding an effective magnetic moment mu(eff)= 4.16 mu(B)comparable to the expected value of mu(eff)= 4.24 mu(B)per Co2RuO4. Using T-N,theta and high temperature series for chi, dominant exchange constant J(1)/k(B)similar to 6 K between the Co(2+)on theA-sites is estimated. Analysis of the ac magnetic susceptibilities near T-SG yields the dynamical critical exponent z nu= 5.2 and microscopic spin relaxation time tau(0)similar to 1.16 x 10(-10)sec characteristic of cluster spin-glasses and the observed time-dependence ofM(t) is supportive of the spin-glass state. LargeM-Hloop asymmetry at low temperatures with giant exchange bias effect (H-EB similar to 1.8 kOe) and coercivity (H-C similar to 7 kOe) for a field cooled sample further support the mixed magnetic phase nature of this interesting spinel. The negative magnetocaloric effect observed belowT(N)is interpreted to be due to the AFM and SG ordering. It is argued that the observed change from positive MCE (magnetocaloric effect) forT>T(N)to inverse MCE forT
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| 11. |
- Linnell, Stephanie F., et al.
(author)
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Enhanced oxygen redox reversibility and capacity retention of titanium-substituted Na-4/7[1/7Ti1/7Mn5/7]O-2 in sodium-ion batteries
- 2022
-
In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:18, s. 9941-9953
-
Journal article (peer-reviewed)abstract
- Anion redox reactions offer a means of enhancing the capacity of layered sodium transition metal oxide positive electrode materials. However, oxygen redox reactions typically show limited reversibility and irreversible structural changes upon cycling, resulting in rapid capacity loss. Here, the Ti-substituted Na-4/7[1/7Ti1/7Mn5/7]O-2 (where represents a transition metal vacancy) is presented as a positive electrode material for sodium-ion batteries. Na-4/7[1/7Ti1/7Mn5/7]O-2 delivers a reversible capacity of 167 mA h g(-1) after 25 cycles at 10 mA g(-1) within the voltage range of 1.6-4.4 V and presents enhanced stability compared with Na-4/7[Mn-1/7(6/7)]O-2 over the voltage range 3.0-4.4 V. The structural and electronic structural changes of this Ti4+ substituted phase are investigated by powder X-ray diffraction, X-ray absorption spectroscopy, electron paramagnetic resonance and Raman spectroscopy, supported by density functional theory calculations. These results show that the Na-4/7[Mn-1/7(6/7)]O-2 structure is maintained between 3.0 and 4.4 V, and the presence of TiO6 octahedra in Na-4/7[1/7Ti1/7Mn5/7]O-2 relieves structural distortions from Jahn-Teller distorted Mn3+O6 between 1.6 and 4.4 V. Furthermore, Ti4+ substitution stabilises the adjacent O 2p orbitals and raises the ionicity of the Mn-O bonds, increasing the operating potential of Na-4/7[1/7Ti1/7Mn5/7]O-2. Thereby providing evidence that the improved electrochemical performance of Na-4/7[1/7Ti1/7Mn5/7]O-2 can be attributed to Ti4+ substitution. This work provides insight and strategies for improving the structural stability and electrochemical performance of sodium layered oxides.
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| 12. |
- Pramanik, Arindam, et al.
(author)
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Dirac states in the noncentrosymmetric superconductor BiPd
- 2021
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In: Physical Review B. - 2469-9950. ; 103:15
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Journal article (peer-reviewed)abstract
- Quantum materials having Dirac fermions in conjunction with superconductivity is believed to be the candidate material to realize exotic physics as well as advanced technology. Angle-resolved photoemission spectroscopy (ARPES), a direct probe of the electronic structure, has been extensively used to study these materials. However, experiments often exhibit conflicting results on dimensionality and momentum of the Dirac fermions (e.g., Dirac states in BiPd, a novel noncentrosymmetric superconductor), which is crucial for the determination of the symmetry, time-reversal invariant momenta, and other emerging properties. Employing high-resolution ARPES at varied conditions, we demonstrated a methodology to identify the location of the Dirac node accurately and discover that the deviation from two dimensionality of the Dirac states in BiPd proposed earlier is not a material property. These results helped to reveal the topology of the anisotropy of the Dirac states accurately. We have constructed a model Hamiltonian considering higher-order spin-orbit terms and demonstrate that this model provides an excellent description of the observed anisotropy. Intriguing features of the Dirac states in a noncentrosymmetric superconductor revealed in this study are expected to have significant implications regarding the properties of topological superconductors.
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| 13. |
- Pramanik, Arindam, et al.
(author)
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Surface states in noncentrosymmetric superconductor BiPd
- 2022
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2164
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Conference paper (peer-reviewed)abstract
- BiPd is a noncentrosymmetric superconductor with Dirac-like surface states on both (010) and (01¯0) faces. The Dirac cone on (010) surface is intense and appears at 0.66 eV binding energy. These states have drawn much attention due to contradictory reports on dimensionality and the momentum of these Dirac fermions. We have studied the properties of these Dirac fermions using varied photon energies and different experimental conditions. The behavior of the Dirac cone is found to be two-dimensional. In addition, we found few more surface states appearing at higher binding energies compared to the Dirac cone.
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| 14. |
- Zhu, Geyunjian H., et al.
(author)
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Feasibility of Coacervate-Like Nanostructure for Instant Drug Nanoformulation
- 2023
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 15:14, s. 17485-17494
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Journal article (peer-reviewed)abstract
- Despite the enormous advancements in nanomedicine research, a limited number of nanoformulations are available on the market, and few have been translated to clinics. An easily scalable, sustainable, and cost-effective manufacturing strategy and long-term stability for storage are crucial for successful translation. Here, we report a system and method to instantly formulate NF achieved with a nanoscale polyelectrolyte coacervate-like system, consisting of anionic pseudopeptide poly(L-lysine isophthalamide) derivatives, polyethylenimine, and doxorubicin (Dox) via simple "mix-and-go" addition of precursor solutions in seconds. The coacervate-like nanosystem shows enhanced intracellular delivery of Dox to patient-derived multidrug-resistant (MDR) cells in 3D tumor spheroids. The results demonstrate the feasibility of an instant drug formulation using a coacervate-like nanosystem. We envisage that this technique can be widely utilized in the nanomedicine field to bypass the special requirement of large-scale production and elongated shelf life of nanomaterials.
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