Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 104(8), p.085106_1 - 085106_12, 2021/08
Times Cited Count:4 Percentile:27.02(Materials Science, Multidisciplinary)Antiferromagnetism in a prototypical quantum critical metal CeCoIn is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn
, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn
by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates
indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature
. At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature
, and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5 T, reducing the volume of the AFM regions. Consequently, a short ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.
Lessux, G. G.*; Sakai, Hironori; Hattori, Taisuke*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Thompson, J. D.*; Pagliuso, P. G.*; Urbano, R. R.*
Physical Review B, 101(16), p.165111_1 - 165111_6, 2020/04
Times Cited Count:8 Percentile:41.75(Materials Science, Multidisciplinary)CeRhIn is a Kondo-lattice prototype in which a magnetic field
31T induces an abrupt Fermi-surface (FS) reconstruction and pronounced in-plane electrical transport anisotropy all within its antiferromagnetic state. Here we report low-temperature nuclear magnetic resonance (NMR) measurements revealing a pronounced decrease in the
In formal Knight shift, without changes in crystal or magnetic structures, of CeRhIn
at fields (
) spanning
. We discuss the emergent state above
in terms of a change in Ce's 4
orbitals that arises from field-induced evolution of crystal-electric field (CEF) energy levels. This change in orbital character enhances hybridization between the 4
and the conduction electrons that leads ultimately to an itinerant quantum-critical point at
50T.
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Fisk, Z.*; et al.
JPS Conference Proceedings (Internet), 30, p.011169_1 - 011169_6, 2020/03
Uranium disulfide -US
showing a semimetal-to-semiconductor crossover has been investigated by the nuclear magnetic resonance (NMR) technique for
S nuclei with the nuclear spin of
. Since the natural concentration 0.76% of NMR active
S nuclei is too dilute, the isotopic enrichment to
50% has been carried out for the single crystal growth. The
S NMR spectra have been successfully obtained using a single crystal of
-US
with external fields along the crystallographic
axis. The S sites assignments have been made based on these NMR spectra.
Sakai, Hironori; Urbano, R. R.*; Tokunaga, Yo; Kambe, Shinsaku; Suzuki, Michito; Kuhns, P. L.*; Reyes, A. P.*; Tobash, P. H.*; Ronning, F.*; Bauer, E. D.*; et al.
Physical Review Letters, 112(23), p.236401_1 - 236401_5, 2014/06
Times Cited Count:7 Percentile:47.75(Physics, Multidisciplinary)Very high field Si-NMR measurements using a fully
Si-enriched URu
Si
single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the
Si shift,
. Moreover, a strong enhancement of
develops near a critical field
T, and the
Si-NMR signal disappears suddenly at
, indicating the total suppression of the HO state. Nevertheless, a weak and shifted
Si-NMR signal reappears for fields higher than
at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.
Bauer, E. D.*; Yang, Y.-F.*; Capan, C.*; Urbano, R. R.*; Miclea, C. F.*; Sakai, Hironori; Ronning, F.*; Graf, M. J.*; Balatsky, A. V.*; Movshovich, R.*; et al.
Proceedings of the National Academy of Sciences of the United States of America, 108(17), p.6857 - 6861, 2011/04
Times Cited Count:39 Percentile:82.04(Multidisciplinary Sciences)Here, we report a manifestation of electronic inhomogeneity in a strongly correlated -electron system, using CeCoIn
as an example. A thermodynamic analysis of its superconductivity, combined with nuclear quadrupole resonance measurements, shows that nonmagnetic impurities (Y, La, Yb, Th, Hg, and Sn) locally suppress unconventional superconductivity, generating an inhomogeneous electronic "Swiss cheese" due to disrupted periodicity of the Kondo lattice. Our analysis may be generalized to include related systems, suggesting that electronic inhomogeneity should be considered broadly in Kondo lattice materials.
Mounce, A. M.*; Oh, S.*; Mukhopadhyay, S.*; Halperin, W. P.*; Reyes, A. P.*; Kuhns, P. L.*; Fujita, Kazuhiro*; Ishikado, Motoyuki; Uchida, Shinichi*
Nature Physics, 7(2), p.125 - 128, 2011/02
Times Cited Count:8 Percentile:49.89It has been predicted that superconducting vortices should be electrically charged and that this effect is particularly enhanced for high-temperature superconductors. Hall effect and nuclear magnetic resonance (NMR) experiments suggest the existence of charge accumulation in the vortex core, but the effects are small and the interpretation controversial. Here we show that the Abrikosov vortex lattice, characteristic of the mixed state of superconductors, will become unstable at a sufficiently high magnetic field if there is charge trapped on the vortex core. Our NMR measurements of the magnetic fields generated by vortices in BiSr
CaCu
O
single crystals provide evidence for an electrostatically driven vortex lattice reconstruction with the magnitude of charge on each vortex pancake of
, depending on doping, in line with theoretical estimates.
Mounce, A. M.*; Oh, S.*; Mukhopadhyay, S.*; Halperin, W. P.*; Reyes, A. P.*; Kuhns, P. L.*; Fujita, Kazuhiro*; Ishikado, Motoyuki; Uchida, Shinichi*
Physical Review Letters, 106(5), p.057003_1 - 057003_4, 2011/02
Times Cited Count:8 Percentile:49.89(Physics, Multidisciplinary)Competition with magnetism is at the heart of high-temperature superconductivity, most intensely felt near a vortex core. To investigate vortex magnetism we have developed a spatially resolved probe based upon NMR spin-lattice-relaxation spectroscopy. With this approach we have found a spin-density wave associated with the vortex core in BiSr
CaCu
O
, similar to checkerboard patterns in the local density of electronic states reported from scanning tunneling microscope experiments. We have determined both the spin-modulation amplitude and decay length from the vortex core in fields up to
= 30 T.
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
no journal, ,
Substitutions of In sites by Zn atoms in heavy fermion superconductor CeCoIn is reported to induce an antiferromagnetic order by Yokoyama et al. in Ibaraki University. Near the critical region, non-Fermi-liquid behavior has been observed in magnetization and specific heat. We have performed NMR measurements to reveal the spin fluctuations near the critical region.
Sakai, Hironori; Hattori, Taisuke; Higa, Nonoka; Tokunaga, Yo; Tateiwa, Naoyuki; Yamamoto, Etsuji; Haga, Yoshinori; Kambe, Shinsaku; Reyes, A. P.*; Bauer, E. D.*; et al.
no journal, ,
-US
is a paramagnetic narrow-gap semiconductor with the energy band gap of 90 K. A characteristic feature of
-US
is the strong response of the electrical resistivity to magnetic field. On the other hand, ferromagnetism is easily induced by pressure of about 1 GPa. Consequently, it is considered to be close to a ferromagnetic instability. To elucidate microscopically this very sensitive electronic states to external fields,
S-NMR study has been performed. We will show our recent
S-NMR results and discuss the electronic states.
Sakai, Hironori; Urbano, R. R.*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
no journal, ,
In order to microscopically investigate what happens around 22 T and just above
36 T in the lowest temperature, we have performed
Si-NMR shift measurement using a
Si-fully-enriched single crystal of URu
Si
. We have found a shift anomaly around 22 T and a critical increase toward
36 T, corresponding to a slight change of total density of states (DOS) at
22 T and increase of DOS toward
36 T. Although the
Si-NMR signal was lost by field sweeping just above
36 T at the lowest temperature, the
Si-NMR spectrum has been successfully obtained at 4.2 K in the magnetic phase just above
36 T. From the spectral shape, we will discuss a possible magnetic structure in the magnetic phase.
Sakai, Hironori; Higa, Nonoka; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Tateiwa, Naoyuki; Haga, Yoshinori; Rossa, P. F. S.*; Thompson, J. D.*; Ronning, F.*; et al.
no journal, ,
-US
is known as a narrow-gap semiconductor. The magnetoresistance in this compound is extremely large but anisotropic. To obtain microscopic view of the magnetism, we have carried on
S-NMR study. We will discuss the magnetic properties in this system to show the recent NMR results.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Bauer, E. D.*
no journal, ,
Uranium disulfide -US
is a paramagnetic semiconductor with a narrow band gap of 90 K at low temperatures, whereas above 80 K it is a semimetal with an extremely low density of carriers. Another characteristic feature in
-US
is the strong response of the electrical resistivity to magnetic field. The magnetoresistance is similar to that of colossal magnetoresistance materials but very anisotropic. In order to clarify the microscopic spin dynamics in
-US
, nuclear magnetic resonance experiments have been performed. Since the natural concentration of
S nuclei (
) is only 0.76%, isotopic enrichment to 50% has been carried out. In the presentation, we would like to discuss about the microscopic magnetism in
-US
to show the NMR results under high fields.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Urbano, R. R.*; Kuhns, P. L.*; Reyes, A. P.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
no journal, ,
The heavy fermion superconductor URuSi
with
K shows the "hidden order" at
K. Below 1 K, it shows a first-order-transition at
T from the hidden order phase to the magnetically ordered phase. The
-
phase diagram for URu
Si
above 35 T is known to be complicated but the details in the each phase above 35 T are unknown. We have been investigating the electronic state by means of
Si-NMR in the higher field. The NMR experiment was done at National High Magnetic Field Laboratory (Tallahassee, FL, U.S.A.).
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Ramakrishna, S. K.*; Reyes, A. P.*; Kotegawa, Hisashi*; To, Hideki*; et al.
no journal, ,
In heavy fermion superconductor CeCoIn, slight Zn substitutions for In atoms induce antiferromagnetism, while slight Ni substitutions for Co atoms suppress superconductivity. The both substituted CeCoIn
exhibit non- fermi-liquid behaviors near the phase boundaries which have been detected by magnetization and specific heat measurements. We have performed NMR experiments in these systems to investigate the microscopic effects by substituents. We will discuss about the spin fluctuations near the boundaries by NMR relaxation rates.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Thompson, J. D.*; Ronning, F.*; Fisk, Z.*; Bauer, E. D.*
no journal, ,
To investigate the microscopic magnetism for -US
, we have performed the nuclear magnetic resonance (NMR) experiments under high fields. Isotopic enrichment of
S nuclei has been attempted to gain the NMR sensitivity. In this presentation, we will discuss about the relationship between the microscopic magnetism and electrical conductivity in
-US
.