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Odd-parity electronic order near the semiconductor limit
Authors:
Jack Tregidga,
Dibyata Rout,
Johannes Hielscher,
Josiah Turner,
Stephen D. Wilson,
John W. Harter
Abstract:
Identifying materials platforms in which dilute carriers experience strong Coulomb interactions is a central challenge in the search for interaction-driven quantum phases. In such systems, weak carrier screening can promote a variety of collective instabilities beyond the conventional Fermi liquid paradigm, including superconductivity, Wigner crystallization, and odd-parity electronic order. Exper…
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Identifying materials platforms in which dilute carriers experience strong Coulomb interactions is a central challenge in the search for interaction-driven quantum phases. In such systems, weak carrier screening can promote a variety of collective instabilities beyond the conventional Fermi liquid paradigm, including superconductivity, Wigner crystallization, and odd-parity electronic order. Experimental realizations of such dilute, strongly interacting electronic systems remain rare in crystalline materials. Here we report a spontaneous odd-parity phase transition in the phosphide semiconductor family $\textit{Ln}$Cd$_3$P$_3$ ($\textit{Ln}$ = La, Ce, Pr, Nd). Using optical second harmonic generation, we observe the onset of bulk inversion and rotational symmetry breaking accompanied by the emergence of an in-plane polar axis. Second harmonic microscopy reveals three domain variants related by 120$^\circ$ rotations, while ultrafast transient reflectivity measurements uncover a pronounced electronic reconstruction across the transition. Remarkably, the ordered phase appears only in lightly self-hole-doped compounds and is absent in insulating SmCd$_3$P$_3$, indicating an essential role for itinerant carriers despite their extremely low concentration. Guided by density functional theory, we develop a four-band model of the valence states and show that modest interactions can stabilize odd-parity electronic order. The resulting phase combines a spontaneous Fermi surface distortion with a momentum-dependent bilayer polarization that breaks inversion symmetry. Our results establish a route to interaction-driven parity breaking in dilute-carrier semiconductors and identify honeycomb bilayer systems as a promising platform for odd-parity electronic phases.
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Submitted 24 June, 2026;
originally announced June 2026.
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Raman scattering spectroscopic observation of a ferroelastic crossover in bond-frustrated PrCd$_3$P$_3$
Authors:
Jackson Davis,
Jesse Liebman,
Dibyata Rout,
S. J. Gomez Alvarado,
Stephen D. Wilson,
Natalia Drichko
Abstract:
2D magnetism in triangular lattices has already shown potential for hosting exotic magnetic states. Control of these magnetic states, both in terms of magnetic properties and in terms of charge doping would be the next step. This makes materials which combine triangular lattice magnetic layers with layers hosting interesting structural or electronic properties particularly useful. PrCd$_3$P$_3$, s…
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2D magnetism in triangular lattices has already shown potential for hosting exotic magnetic states. Control of these magnetic states, both in terms of magnetic properties and in terms of charge doping would be the next step. This makes materials which combine triangular lattice magnetic layers with layers hosting interesting structural or electronic properties particularly useful. PrCd$_3$P$_3$, studied in this work, is one of a family of materials where triangular lattice layers of magnetic rare earth ions alternate with semiconducting hexagonal CdP layers. Using Raman scattering spectroscopy we uncover a structural instability in the CdP layers, associated with a soft mode behavior of a phonon in these layers. Raman scattering detects crystal electric field excitations, and confirms a singlet ground state for Pr$^{3+}$ and splitting of the doublet levels as a result of the structural instability in CdP layers. While Pr$^{3+}$ is non-magnetic in PrCd$_3$P$_3$ we speculate that this family of materials can realize control of the magnetic layer through the CdP layer which can become ferroelectric under strain that would relieve frustration.
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Submitted 4 March, 2026;
originally announced March 2026.
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Emergent Random Spin Singlets in Disordered Spin-1/2 perovskite BaCu$_{1/3}$Ta$_{2/3}$O$_3$
Authors:
Sagar Mahapatra,
Francesco De Angelis,
Dibyata Rout,
Priyanshi Tiwari,
Martin Etter,
Edmund Welter,
M. P. Saravanan,
Rajeev Rawat,
Satoshi Nishimoto,
Carlo Meneghini,
Surjeet Singh
Abstract:
We investigate the disordered perovskite BaCu$_{1/3}$Ta$_{2/3}$O$_3$, where Cu (spin-1/2) and Ta randomly occupy a pseudo-cubic lattice. Synchrotron X-ray diffraction and X-ray absorption spectroscopy establish the local nature of the disorder, revealing the presence of structurally constrained magnetic exchange paths. No magnetic ordering or spin freezing is observed down to 0.1 K. The low-temper…
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We investigate the disordered perovskite BaCu$_{1/3}$Ta$_{2/3}$O$_3$, where Cu (spin-1/2) and Ta randomly occupy a pseudo-cubic lattice. Synchrotron X-ray diffraction and X-ray absorption spectroscopy establish the local nature of the disorder, revealing the presence of structurally constrained magnetic exchange paths. No magnetic ordering or spin freezing is observed down to 0.1 K. The low-temperature magnetic and thermodynamic behavior is captured by a broad but non-singular distribution $P(J)$ of exchange couplings $J$. These results open the possibility of realizing a disordered quantum ground state where the exchange randomness is broad yet intrinsically bounded, departing from the conventional infinite-randomness fixed point driven random-singlet phase.
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Submitted 24 January, 2026;
originally announced January 2026.
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Interplay of phonons, intertwined density waves, and induced spin density wave in trilayer nickelates Pr4-xLaxNi3O10
Authors:
Sonia Deswal,
Dibyata Rout,
Nirmalya Jana,
Koushik Pal,
Surjeet Singh,
Pradeep Kumar
Abstract:
Lattice degrees of freedom (DoF) play a central role in correlated electron systems, strongly influencing the dynamics of the underlying charge carriers and spin excitations. In nickelates, understanding the role of lattice is essential to unravel the interplay between charge, orbital, and spin degree of freedom in giving rise to various emergent phenomena reported recently. Here, we investigate t…
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Lattice degrees of freedom (DoF) play a central role in correlated electron systems, strongly influencing the dynamics of the underlying charge carriers and spin excitations. In nickelates, understanding the role of lattice is essential to unravel the interplay between charge, orbital, and spin degree of freedom in giving rise to various emergent phenomena reported recently. Here, we investigate the phononic DoF in a series of trilayer nickelates, namely Pr4-xLaxNi3O10 (where x = 0, 0.4, 1, 2, 3.6, and 4) using temperature and polarization dependent Raman scattering measurements. Our in-depth analysis of the phonon evolution with temperature and doping, gives interesting insights into the behaviour of these materials. All these systems undergo a metal-to-metal transition (TMMT), characterized by the development of intertwined spin and charge density waves, with the spin density wave preceding the charge density wave. These transitions manifest as pronounced anomalies in phonon self-energy parameters i.e. peak frequency and linewidth in the vicinity of the metal-to-metal transition. Several phonon modes show dramatic change (nearly an order of magnitude for some modes) in their softening rates across the TMMT, highlighting the sensitivity of the lattice dynamics to spin and charge order. These findings emphasize the crucial role of lattice DoF in mediating correlated ground states in layered nickelates.
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Submitted 2 December, 2025;
originally announced December 2025.
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Hidden frustration in the triangular-lattice antiferromagnet NdCd3P3
Authors:
Juan R. Chamorro,
Steven J. Gomez Alvarado,
Dibyata Rout,
Sarah Schwarz,
Allen Scheie,
Ganesh Pokharel,
Alexander I. Kolesnikov,
Lukas Keller,
Stephen D. Wilson
Abstract:
We report a study of the magnetic ground state and crystal electric field (CEF) scheme in the triangular-lattice antiferromagnet NdCd$_3$P$_3$. Combined neutron scattering, magnetization, and heat capacity measurements demonstrate that the Nd$^{3+}$ moments occupying the triangular lattice in this material harbor hidden signs of frustration not detected in typical Curie-Weiss-based parameterizatio…
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We report a study of the magnetic ground state and crystal electric field (CEF) scheme in the triangular-lattice antiferromagnet NdCd$_3$P$_3$. Combined neutron scattering, magnetization, and heat capacity measurements demonstrate that the Nd$^{3+}$ moments occupying the triangular lattice in this material harbor hidden signs of frustration not detected in typical Curie-Weiss-based parameterization of the frustration index ($f=Θ_{CW} / T_N$). This is evidenced by a zero-field splitting of the Kramers' ground state and first excited state doublets at temperatures far in excess of $T_N$ as well as signatures of low-energy fluctuations for $T>>T_N$. A suppression of the zero-field ordered moment relative to its field saturation value is observed, and the impacts of this magnetic frustration as well as the coexisting bond frustration in the CdP honeycomb network on the physical properties of NdCd$_3$P$_3$ are discussed.
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Submitted 9 September, 2025;
originally announced September 2025.
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High-pressure floating zone crystal growth of Sr$_2$IrO$_4$
Authors:
S. J. Gomez Alvarado,
Y. Pang,
P. A. Barrera,
D. Rout,
C. Robison,
Z. Porter,
H. Z. Porter,
E. A. Lawrence,
E. N. Bassey,
S. D. Wilson
Abstract:
Here we demonstrate the floating zone crystal growth of the $J_\mathrm{eff}=1/2$ Mott insulator Sr$_2$IrO$_4$. Historically, the growth of iridates from a ternary melt has been precluded by the extreme vapor pressure of the metal oxide species and the difficulty of maintaining the correct oxidation state of Ir at high temperatures. Here, we show that the application of a high-pressure oxygen growt…
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Here we demonstrate the floating zone crystal growth of the $J_\mathrm{eff}=1/2$ Mott insulator Sr$_2$IrO$_4$. Historically, the growth of iridates from a ternary melt has been precluded by the extreme vapor pressure of the metal oxide species and the difficulty of maintaining the correct oxidation state of Ir at high temperatures. Here, we show that the application of a high-pressure oxygen growth environment stabilizes the Sr$_2$IrO$_4$ phase, leading to the first demonstration of cm$^{3}$-scale crystals. In contrast to the conventional SrCl$_2$ flux growth method, where poor control over disorder leads to strong sample dependence, the high-pressure floating zone growth enables active control over the homogeneity of the melt. Crystals grown via this technique possess qualitatively similar properties to those grown via flux, with a relatively sharp onset of antiferromagnetic order observed in temperature-dependent magnetization. Further, we demonstrate that by tuning the mixing rate of the melt, we are able to grow natively hole-doped Sr$_2$Ir$_{1-y}$O$_4$, which exhibits a strongly modified magnetic and electronic response.
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Submitted 17 May, 2025; v1 submitted 16 February, 2025;
originally announced February 2025.
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Interleaved bond frustration in a triangular lattice antiferromagnet
Authors:
S. J. Gomez Alvarado,
J. R. Chamorro,
D. Rout,
J. Hielscher,
Sarah Schwarz,
Caeli Benyacko,
M. B. Stone,
V. Ovidiu Garlea,
A. R. Jackson,
G. Pokharel,
R. Gomez,
B. R. Ortiz,
Suchismita Sarker,
L. Kautzsch,
L. C. Gallington,
R. Seshadri,
Stephen D. Wilson
Abstract:
Frustration of long-range order via lattice geometries serves to amplify fluctuations of the order parameter and generate unconventional ground states that are highly sensitive to perturbations. Traditionally, this concept of geometric frustration is used to engineer unconventional magnetic states in a variety of materials; however, the charge degree of freedom and bond order can be similarly frus…
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Frustration of long-range order via lattice geometries serves to amplify fluctuations of the order parameter and generate unconventional ground states that are highly sensitive to perturbations. Traditionally, this concept of geometric frustration is used to engineer unconventional magnetic states in a variety of materials; however, the charge degree of freedom and bond order can be similarly frustrated. Finding materials that host both frustrated magnetic and bond networks holds promise for engineering structural and magnetic states with the potential of coupling to one another via either the magnetic sector (via magnetic field) or via the lattice sector (via strain). In this paper, we identify an unusual instance of this coexistence in the triangular lattice antiferromagnetic compounds $Ln$Cd$_3$P$_3$ ($Ln$ = La, Ce, Pr, and Nd). These compounds feature two-dimensional planes of unique trigonal-planar CdP$_3$ units that manifest an underlying bond instability with its long-range ordering frustrated via emergent kagome ice bond correlations. Our results establish $Ln$Cd$_3$P$_3$ as a rare class of materials where frustrated magnetism across a tunable rare-earth triangular network is embedded within a dopable semiconductor with a frustrated bond order instability.
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Submitted 22 October, 2025; v1 submitted 7 January, 2025;
originally announced January 2025.
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Dynamics of electron-electron correlated to electron-phonon coupled phase progression in trilayer nickelate La4Ni3O10
Authors:
Sonia Deswal,
Deepu Kumar,
Dibyata Rout,
Surjeet Singh,
Pradeep Kumar
Abstract:
Trilayer nickelates are a rich class of materials exhibiting diverse correlated phenomena, including superconductivity, density wave transitions, non-Fermi liquid behavior along with an unusual metal-to-metal transition around T* ~ 150 K. Understanding the electronic correlations, lattice and charge dynamics are crucial to unreveal the origin of superconductivity and other instabilities in nickela…
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Trilayer nickelates are a rich class of materials exhibiting diverse correlated phenomena, including superconductivity, density wave transitions, non-Fermi liquid behavior along with an unusual metal-to-metal transition around T* ~ 150 K. Understanding the electronic correlations, lattice and charge dynamics are crucial to unreveal the origin of superconductivity and other instabilities in nickelates. Our in-depth Raman measurements shows that trilayer nickelate, La4Ni3O10, shows transition from electron-phonon coupled phase to the electron-electron correlated one below charge density wave transition around T* with an estimated energy gap of ~ 18-20 meV. The transition around T* is also accompanied by the emergence of zone folded phonon modes reflecting the transition into the charge density wave phase. Phonon modes self-energy parameters show anomalous changes around T* attributed to the electron-electron correlations, and renormalization rate of the phonon modes is much slower in the charge-ordered phase compared to the phase above T*. The transition around T* are marked by the suppression of electron-phonon coupling parameter by ~ 70 %, a change of the quasiparticle dynamics from non-Fermi liquid to the Landau-Fermi liquid type behaviour estimated using the low frequency Raman response.
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Submitted 21 November, 2024;
originally announced November 2024.
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Investigating the cause of crossover from charge/spin stripe insulator to correlated metallic phase in layered T' nickelates -- R$_4$Ni$_3$O$_8$
Authors:
Dibyata Rout,
Sanchayeta Ranajit Mudi,
Suman Karmakar,
Rajeev Rawat,
Surjeet Singh
Abstract:
The $T^{\prime}$ infinite layered nickelates have recently garnered significant attention owing to the discovery of superconductivity in hole-doped RNiO$_2$ (R $=$ La, Pr, or Nd), which is the $n = \infty$ member of the series R$_{n+1}$Ni$_n$O$_{2n+2}$. Here, we investigate the $n = 3$ member, namely R$_4$Ni$_3$O$_8$ (R $=$ La, Pr, or Nd) of this family. The compound La$_4$Ni$_3$O$_8$ exhibits sim…
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The $T^{\prime}$ infinite layered nickelates have recently garnered significant attention owing to the discovery of superconductivity in hole-doped RNiO$_2$ (R $=$ La, Pr, or Nd), which is the $n = \infty$ member of the series R$_{n+1}$Ni$_n$O$_{2n+2}$. Here, we investigate the $n = 3$ member, namely R$_4$Ni$_3$O$_8$ (R $=$ La, Pr, or Nd) of this family. The compound La$_4$Ni$_3$O$_8$ exhibits simultaneous charge/spin-stripe ordering at T$_N^\ast$ $=$ 105 K, which is also concomitant with the onset of metal-to-insulator (MIT) transition upon lowering the temperature below T$_N^\ast$. We investigate the conspicuous absence of this transition in the Pr and Nd analogues of La$_4$Ni$_3$O$_8$. To achieve this purpose, we synthesized solid-solutions of the form (La, Pr)$_4$Ni$_3$O$_8$ and (La, Nd)$_4$Ni$_3$O$_8$ and examined the behavior of T$_N^\ast$ as a function of the average R-site ionic radius ($r_{\overline{R}}$). We show that after an initial quasilinear decrease with decreasing $r_{\overline{R}}$, T$_N^\ast$ suddenly vanishes in the narrow range 1.134 $Å$ $\leq$ $r_{\overline{R}}$ $\leq$ 1.143 $Å$. In the same range, we observed the emergence of a new transition below T$^\ast$, whose onset temperature increases as $r_{\overline{R}}$ further decreases. We, therefore, argue that the sudden vanishing of charge/spin-stripe/MIT ordering upon decreasing $r_{\overline{R}}$ is due to the appearance of a new competing phase. The point $r_{\overline{R}}$ $\approx$ $r_c$, where T$_N^\ast$ vanishes and T$^\ast$ appears -- a quantum critical point -- should be investigated further. In this regard, Pr$_4$Ni$_3$O$_8$ and Pr-rich samples should be useful due to the weak magnetization response associated with the Pr-sublattice, as shown here.
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Submitted 9 November, 2023;
originally announced November 2023.
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Evidence of Charge-Phonon coupling in Van der Waals materials Ni1-xZnxPS3
Authors:
Nashra Pistawala,
Ankit Kumar,
Devesh Negi,
Dibyata Rout,
Luminita Harnagea,
Surajit Saha,
Surjeet Singh
Abstract:
NiPS3 is a Van der Waals antiferromagnet that has been found to display spin-charge and spin-phonon coupling in its antiferromagnetically ordered state below TN = 155 K. Here, we study high-quality crystals of site-diluted Ni1-xZnxPS3 (0 < x < 0.2) using temperature-dependent specific heat and Raman spectroscopy probes. The site dilution suppresses the antiferromagnetic ordering in accordance with…
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NiPS3 is a Van der Waals antiferromagnet that has been found to display spin-charge and spin-phonon coupling in its antiferromagnetically ordered state below TN = 155 K. Here, we study high-quality crystals of site-diluted Ni1-xZnxPS3 (0 < x < 0.2) using temperature-dependent specific heat and Raman spectroscopy probes. The site dilution suppresses the antiferromagnetic ordering in accordance with the mean-field prediction. In NiPS3, we show that the phonon mode P2 (176 cm-1) associated with Ni vibrations show a distinct asymmetry due to the Fano resonance, which persists only in the paramagnetic phase, disappearing below T_N = 155 K. This was further supported by temperature-dependent Raman data on an 8% Zn-doped crystal (T_N = 135 K) where Fano resonance similarly van in the magnetically ordered phase. This is contrary to the behaviour of the Raman mode P9 (570 cm-1), which shows a Fano resonance at low temperatures below T_N due to its coupling with the two-magnon continuum. We show that the Fano resonance of P2 arises from its coupling with an electronic continuum that weakens considerably upon cooling to low temperatures. In the doped crystals, the Fano coupling is found to enhance with Zn-doping. These observations suggest the presence of strong electron-phonon coupling in the paramagnetic phase of NiPS3 due to charge density fluctuations associated with the negative charge transfer state of Ni.
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Submitted 25 July, 2023; v1 submitted 24 July, 2023;
originally announced July 2023.
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Optically induced symmetry breaking due to nonequilibrium steady state formation in charge density wave material 1T-TiSe2
Authors:
Harshvardhan Jog,
Luminita Harnagea,
Dibyata Rout,
Takashi Taniguchi,
Kenji Watanabe,
Eugene J. Mele,
Ritesh Agarwal
Abstract:
The strongly correlated charge density wave (CDW) phase of 1T-TiSe$_2$ is being extensively researched to verify the claims of a unique chiral order due to the presence of three equivalent Fermi wavevectors involved in the CDW formation. Characterization of the symmetries is therefore critical to understand the origin of their intriguing properties but can be complicated by the coupling of the ele…
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The strongly correlated charge density wave (CDW) phase of 1T-TiSe$_2$ is being extensively researched to verify the claims of a unique chiral order due to the presence of three equivalent Fermi wavevectors involved in the CDW formation. Characterization of the symmetries is therefore critical to understand the origin of their intriguing properties but can be complicated by the coupling of the electronic and lattice degrees of freedom. Here we use continuous wave laser excitation to probe the symmetries of TiSe$_2$ using the circular photogalvanic effect with very high sensitivity. We observe that the ground state of the CDW phase is achiral. However, laser excitation above a threshold intensity transforms TiSe$_2$ into a chiral phase in a nonequilibrium steady state, which changes the electronic correlations in the stacking direction of the layered material. The inherent sensitivity of the photogalvanic technique provides clear evidence of the different optically driven phases of 1T-TiSe$_2$, as well as emphasizes the interplay of electronic and lattice degrees of freedom in this system under optical excitation. Our work demonstrates that optically induced phase change can occur at extremely low optical intensities in strongly correlated materials, providing a pathway for future studies to engineer new phases using light.
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Submitted 19 November, 2023; v1 submitted 25 April, 2023;
originally announced April 2023.
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Giant orbital polarization of Ni$^{2+}$ in square planar environment
Authors:
Prithwijit Mandal,
Ranjan Kumar Patel,
Dibyata Rout,
Rajdeep Banerjee,
Rabindranath Bag,
Koushik Karmakar,
Awadhesh Narayan,
John W. Freeland,
Surjeet Singh,
Srimanta Middey
Abstract:
Understanding the electronic behavior of Ni$^{2+}$ in a square planar environment of oxygen is the key to unravel the origin of the recently discovered superconductivity in the hole doped nickelate Nd$_{0.8}$Sr$_{0.2}$NiO$_2$. To identify the major similarities/dissimilarities between nickelate and cuprate superconductivity, the study of the electronic structure of Ni$^{2+}$ and Cu$^{2+}$ in an id…
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Understanding the electronic behavior of Ni$^{2+}$ in a square planar environment of oxygen is the key to unravel the origin of the recently discovered superconductivity in the hole doped nickelate Nd$_{0.8}$Sr$_{0.2}$NiO$_2$. To identify the major similarities/dissimilarities between nickelate and cuprate superconductivity, the study of the electronic structure of Ni$^{2+}$ and Cu$^{2+}$ in an identical square planar environment is essential. In order to address these questions, we investigate the electronic structure of Sr$_2$CuO$_3$ and Ni doped Sr$_2$CuO$_3$ single crystals containing (Cu/Ni)O$_4$ square planar units. Our polarization dependent X-ray absorption spectroscopy experiments for Ni in Sr$_2$Cu$_{0.9}$Ni$_{0.1}$O$_3$ have revealed very large orbital polarization, which is a characteristic feature of high $T_c$ cuprate. This arises due to the low spin $S$=0 configuration with two holes in Ni 3$d_{x^2-y^2}$ orbitals - in contrast to the expected high spin $S$=1 state from Hund's first rule. The presence of such $S$=0 Ni$^{2+}$ in hole doped nickelate would be analogous to the Zhang Rice singlet. However, the Mott Hubbard insulating nature of the NiO$_4$ unit would point towards a different electronic phase space of nickelates, compared to high $T_c$ cuprates.
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Submitted 7 September, 2020;
originally announced September 2020.
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Growth, Properties, and Applications of Pulsed Laser Deposited Nanolaminate Ti3AlC2 Thin Films
Authors:
Abhijit Biswas,
Arundhati Sengupta,
Umashankar Rajput,
Sachin Kumar Singh,
Vivek Antad,
Sk Mujaffar Hossain,
Swati Parmar,
Dibyata Rout,
Aparna Deshpande,
Sunil Nair,
Satishchandra Ogale
Abstract:
Recently, nanolaminated ternary carbides have attracted immense interest due to the concomitant presence of both ceramic and metallic properties. Here, we grow nanolaminate Ti3AlC2 thin films by pulsed laser deposition on c-axis-oriented sapphire substrates and, surprisingly, the films are found to be highly oriented along the (103) axis normal to the film plane, rather than the (000l) orientation…
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Recently, nanolaminated ternary carbides have attracted immense interest due to the concomitant presence of both ceramic and metallic properties. Here, we grow nanolaminate Ti3AlC2 thin films by pulsed laser deposition on c-axis-oriented sapphire substrates and, surprisingly, the films are found to be highly oriented along the (103) axis normal to the film plane, rather than the (000l) orientation. Multiple characterization techniques are employed to explore the structural and chemical quality of these films, the electrical and optical properties, and the device functionalities. The 80-nm thick Ti3AlC2 film is highly conducting at room temperature (resistivity of 50 micro ohm-cm), and a very-low-temperature coefficient of resistivity. The ultrathin (2 nm) Ti3AlC2 film has fairly good optical transparency and high conductivity at room temperature (sheet resistance of 735 ohm). Scanning tunneling microscopy reveals the metallic characteristics (with finite density of states at the Fermi level) at room temperature. The metal-semiconductor junction of the p-type Ti3AlC2 film and n-Si show the expected rectification (diode) characteristics, in contrast to the ohmic contact behavior in the case of Ti3AlC2 on p-Si. A triboelectric-nanogenerator-based touch-sensing device, comprising of the Ti3AlC2 film, shows a very impressive peak-to-peak open-circuit output voltage of 80 V. These observations reveal that pulsed laser deposited Ti3AlC2 thin films have excellent potential for applications in multiple domains, such as bottom electrodes, resistors for high-precision measurements, Schottky diodes, ohmic contacts, fairly transparent ultrathin conductors, and next-generation biomechanical touch sensors for energy harvesting.
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Submitted 9 July, 2020;
originally announced July 2020.
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Structural and physical properties of trilayer nickelates $R_4$Ni$_3$O$_{10}$ ($R =$ La, Pr and Nd)
Authors:
Dibyata Rout,
Sanchayeta Ranajit Mudi,
Marco Hoffmann,
Sven Spachmann,
Rüdiger Klingeler,
Surjeet Singh
Abstract:
We investigate the low temperature structural and physical properties of the trilayer nickelates R4Ni3O10 (R = La, Pr and Nd) using resistivity, thermopower, thermal conductivity, specific heat, high-resolution synchrotron powder X-ray diffraction and thermal expansion experiments. We show that all three compounds crystallize with a monoclinic symmetry, and undergo a metal-to-metal (MMT) transitio…
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We investigate the low temperature structural and physical properties of the trilayer nickelates R4Ni3O10 (R = La, Pr and Nd) using resistivity, thermopower, thermal conductivity, specific heat, high-resolution synchrotron powder X-ray diffraction and thermal expansion experiments. We show that all three compounds crystallize with a monoclinic symmetry, and undergo a metal-to-metal (MMT) transition at 135 K (La), 156 K (Pr) and 160 K (Nd). At MMT, the lattice parameters show distinct anomalies; however, without any lowering of the lattice symmetry. Unambiguous signatures of MMT are also seen in magnetic and thermal measurements, which suggest a strong coupling between the electronic, magnetic and structural degrees of freedom in these nickelates. Analysis of thermal expansion yields hydrostatic pressure dependence of MMT in close agreement with experiments. We show that the 9-fold coordinated Pr ions in the rocksalt (RS) layers have a crystal field (CF) split doublet ground state with possible antiferromagnetic ordering at 5 K. The Pr ions located in the perovskite block (PB) layers with 12-fold coordination, however, exhibit a non-magnetic singlet ground state. The CF ground state of Nd in both RS and PB layers is a Kramers doublet. Heat capacity of R = Nd shows a Schottky-like anomaly near35 K, and an upturn below T = 10 K suggesting the presence of short-range correlations between the Nd moments. However, no signs of long-range ordering could be found down to 2 K despite a sizeable theta_p ~ -40 K. The strongly suppressed magnetic long-range ordering in both R = Pr and Nd suggests the presence of strong magnetic frustration in these compounds. The low-temperature resistivity shows a T^0.5 dependence. No evidence for the heavy fermion behavior could be found in any of the three compounds.
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Submitted 28 January, 2021; v1 submitted 1 July, 2020;
originally announced July 2020.
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Synthesis, magnetic properties and electronic structure of S = 1/2 uniform spin chain system InCuPO5
Authors:
B. Koteswararao,
Binoy K. Hazra,
Dibyata Rout,
P. V. Srinivasarao,
S. Srinath,
S. K. Panda
Abstract:
We have studied the structural, magnetic properties, and electronic structure of the compound InCuPO5 synthesized by solid state reaction method. The structure of InCuPO5 comprises of S = 1/2 uniform spin chains formed by corner-shared CuO4 units. Magnetic susceptibility chi(T) data shows a broad maximum at about 65 K, a characteristic feature of one-dimensional (1D) magnetism. The chi(T) data is…
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We have studied the structural, magnetic properties, and electronic structure of the compound InCuPO5 synthesized by solid state reaction method. The structure of InCuPO5 comprises of S = 1/2 uniform spin chains formed by corner-shared CuO4 units. Magnetic susceptibility chi(T) data shows a broad maximum at about 65 K, a characteristic feature of one-dimensional (1D) magnetism. The chi(T) data is fitted to the coupled, S = 1/2 Heisenberg antiferromagnetic (HAFM) uniform chain model that gives the intra-chain coupling (J/kB) between nearest neighbour Cu2+ ions as -100 K and the ratio of inter-chain to intra-chain coupling (J'/J) as about 0.07. The exchange couplings estimated from the magnetic data analysis are in good agreement with the computed values from the electronic structure calculations based on density functional theory + Hubbard U (DFT+U) approach. The combination of theoretical and experimental analysis confirms that InCuPO5 is a candidate material for weakly coupled S = 1/2 uniform chains. A detailed theoretical analysis of the electronic structure further reveals that the system is insulating with a gap of 2.4 eV and a local moment of 0.70 muB /Cu.
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Submitted 26 May, 2017;
originally announced May 2017.
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Structure and Rheology of the Defect-gel States of Pure and Particle-dispersed Lyotropic Lamellar Phases
Authors:
Geetha Basappa,
Suneel,
V. Kumaran,
Prabhu R. Nott,
Sriram Ramaswamy,
V. M. Naik,
Deeleep Rout
Abstract:
We present important new results from light-microscopy and rheometry on a moderately concentrated lyotropic smectic, with and without particulate additives. Shear-treatment aligns the phase rapidly, except for a striking network of oily-streak defects, which anneals out much more slowly. If spherical particles several microns in diameter are dispersed in the lamellar medium, part of the defect n…
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We present important new results from light-microscopy and rheometry on a moderately concentrated lyotropic smectic, with and without particulate additives. Shear-treatment aligns the phase rapidly, except for a striking network of oily-streak defects, which anneals out much more slowly. If spherical particles several microns in diameter are dispersed in the lamellar medium, part of the defect network persists under shear-treatment, its nodes anchored on the particles. The sample as prepared has substantial storage and loss moduli, both of which decrease steadily under shear-treatment. Adding particles enhances the moduli and retards their decay under shear. The data for the frequency-dependent storage modulus after various durations of shear-treatment can be scaled to collapse onto a single curve. The elasticity and dissipation in these samples thus arises mainly from the defect network, not directly from the smectic elasticity and hydrodynamics.
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Submitted 14 July, 1999; v1 submitted 30 April, 1999;
originally announced April 1999.