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Journal Articles

Feedback of superconductivity on the magnetic excitation spectrum of UTe$$_{2}$$

Raymond, S.*; Knafo, W.*; Knebel, G.*; Kaneko, Koji; Brison, J.-P.*; Flouquet, J.*; Aoki, Dai*; Lapertot, G.*

Journal of the Physical Society of Japan, 90(11), p.113706_1 - 113706_5, 2021/11

Journal Articles

Low-dimensional antiferromagnetic fluctuations in the heavy-fermion paramagnetic ladder compound UTe$$_{2}$$

Knafo, W.*; Knebel, G.*; Steffens, P.*; Kaneko, Koji; Rosuel, A.*; Brison, J.-P.*; Flouquet, J.*; Aoki, Dai*; Lapertot, G.*; Raymond, S.*

Physical Review B, 104(10), p.L100409_1 - L100409_6, 2021/09

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

$$T$$ dependence of nuclear spin-echo decay at low temperatures in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Hattori, Taisuke; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Physical Review B, 95(19), p.195121_1 - 195121_8, 2017/05

AA2017-0083.pdf:0.74MB

 Times Cited Count:3 Percentile:23.04(Materials Science, Multidisciplinary)

The authors report $$^{29}$$Si nuclear spin-echo oscillations and decay measurements on a single crystal of YbRh$$_2$$Si$$_2$$. These quantities are found to be $$T$$ independent from 300 K down to $$sim$$20 K, showing, however, a strong $$T$$ dependence below 20 K. These results indicate that electronic states near the Fermi level are modified at low temperatures. The observed spin-echo oscillations can be interpreted with the Ruderman-Kittel and pseudo-dipolar interactions between nearest-neighbor Si nuclei driven by conduction electron scattering at the Fermi surface. Possible modifications to the Fermi surface at low temperatures are discussed.

Journal Articles

$$^{29}$$Si NMR spin-echo decay in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Hattori, Taisuke; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Journal of Physics; Conference Series, 683(1), p.012006_1 - 012006_7, 2016/02

BB2015-1546.pdf:0.87MB

 Times Cited Count:1 Percentile:60.83

By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time ($$T_1$$) measurements on a single crystal sample YbRh$$_2$$Si$$_2$$, the magnetic excitations around quantum critical phase transition is investigated. It is revealed that the coexisting Fermi and non-Fermi states appears near the quantum critical phase transition. Such a mottled state is considered to have remained hidden in Ce and U heavy fermion compounds, owing presumably to short lifetimes for the two states. The mottled state is highly anisotropic to applied magnetic field, which is consistent with previous studies. The origin of mottled state will be discussed.

Journal Articles

Anisotropic magnetic fluctuations in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Journal of Physics; Conference Series, 592(1), p.012085_1 - 012085_5, 2015/03

 Times Cited Count:2 Percentile:65.76

Recently there is renewed interest in quantum critical phase transitions (QCPT) at $$T=0$$ K in metallic strongly-correlated electron systems. From early experimental results, the QCPT in the Kondo-lattice compound YbRh$$_2$$Si$$_2$$ is not a case of the ordinary spin density wave (SDW) instability observed in Ce-based Kondo-lattices, but a candidate for a novel locally critical case In new observations reported here, we find that coexisting, static Fermi liquid (FL) and non-Fermi liquid (NFL) states are a key feature of the QCPT in YbRh$$_2$$Si$$_2$$. Such a pair of states has remained hidden in Ce compounds, owing presumably to short lifetimes for the two states. A new scaling law for the occupation ratio of the two states is derived, and could be widely applicable to Kondo-lattice systems.

Journal Articles

Degenerate Fermi and non-Fermi liquids near a quantum critical phase transition

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Nature Physics, 10(11), p.840 - 844, 2014/11

 Times Cited Count:17 Percentile:74.1(Physics, Multidisciplinary)

In new observations reported here, we find that coexisting, static Fermi liquid and non-Fermi liquid states are a key feature of the QCPT in YbRh$$_{2}$$Si$$_{2}$$. By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time measurements on a single crystal sample, it is revealed that the FL and NFL states are invariant,while their relative proportion in a crossover is field dependent near the QCPT. Such a pair of states has remained hidden in Ce compounds, owing presumably to short lifetimes for the two states. A new scaling law for the occupation ratio of the two states is derived, and could be widely applicable to Kondo-lattice systems

Journal Articles

Field-induced order in heavy-fermion compound YbCo$$_2$$Zn$$_{20}$$

Kaneko, Koji; Raymond, S.*; Ressouche, E.*; Lapertot, G.*; Takeuchi, Tetsuya*; Hirose, Yusuke*; Honda, Fuminori*; Onuki, Yoshichika

JPS Conference Proceedings (Internet), 3, p.011061_1 - 011061_5, 2014/06

Journal Articles

Anisotropic energy scale for degenerate Fermi and non-Fermi liquids near a quantum critical phase transition in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Physical Review B, 91(16), p.161110_1 - 161110_5, 2014/04

 Times Cited Count:3 Percentile:17.86(Materials Science, Multidisciplinary)

Based on $$^{29}$$Si nuclear spin-lattice relaxation time ($$T_1$$) data on a single crystal of YbRh$$_2$$Si$$_2$$, the coexisting Fermi liquid (FL) and non-Fermi liquid (NFL) states around the quantum critical phase transition have been found to be sensitive to the direction of the applied magnetic field. Augmented scaling analysis shows that the anisotropic characteristic temperature and field are roughly 10 times larger for $$Hparallel c$$ than for $$Hparallel a$$, consistent with a previously obtained anisotropic phase diagram.

Journal Articles

Magnetic polarization and Fermi surface instability; Case of YbRh$$_2$$Si$$_2$$

Pourret, A.*; Knebel, G.*; Matsuda, Tatsuma; Lapertot, G.*; Flouquet, J.*

Journal of the Physical Society of Japan, 82(5), p.053704_1 - 053704_5, 2013/05

 Times Cited Count:28 Percentile:81.38(Physics, Multidisciplinary)

Journal Articles

Observation of bulk band dispersions of YbRh$$_2$$Si$$_2$$ using soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira*; Saito, Yuji; Fujimori, Shinichi; kawasaki, Ikuto*; Okane, Tetsuo; Takeda, Yukiharu; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma*; Haga, Yoshinori; et al.

Physical Review B, 87(7), p.075131_1 - 075131_6, 2013/02

 Times Cited Count:5 Percentile:28.48(Materials Science, Multidisciplinary)

We have performed soft X-ray angle-resolved photoemission spectroscopy (ARPES) measurements on YbRh$$_2$$Si$$_2$$ and clarified its three-dimensional bulk valence-band structures. The ARPES spectra have not only Yb$$^{3+}$$ multiplet peaks but also a finite contribution of Yb$$^{2+}$$ peaks at 15 K, corresponding to the valence fluctuating behavior in this compound. This means that Yb 4f electrons in this compound have itinerant character below the $$T_{rm K}$$. We have found that dispersions of the valence bands except the vicinity of the Yb 4f bands agree better with those of the band-structure calculation of LuRh$$_2$$Si$$_2$$ than those of YbRh$$_2$$Si$$_2$$ within a local-density approximation. In addition, the Yb 3d-4f resonant photoemission spectra of YbRh$$_2$$Si$$_2$$ strongly suggest the existence of Yb 5d electrons in the valence band. We conclude that the charge transfer from the Yb 4f state to the Yb 5d state has an important role in the formation of the valence band of YbRh$$_2$$Si$$_2$$.

Journal Articles

Evidence for three fluctuation channels in the spin resonance of the unconventional superconductor CeCoIn$$_5$$

Raymond, S.*; Kaneko, Koji; Hiess, A.*; Steffens, P.*; Lapertot, G.*

Physical Review Letters, 109(23), p.237210_1 - 237210_5, 2012/12

 Times Cited Count:17 Percentile:70.21(Physics, Multidisciplinary)

Journal Articles

Huge upper critical field in the superconductor with non-centrosymmetric crystal structure CeCoGe$$_3$$

M$'e$asson, M.-A.*; Muranaka, Hiroshi*; Matsuda, Tatsuma; Kawai, Tomoya*; Haga, Yoshinori; Knebel, G.*; Aoki, Dai*; Lapertot, G.*; Honda, Fuminori*; Settai, Rikio*; et al.

Physica C, 470(Suppl.1), p.S536 - S538, 2010/12

 Times Cited Count:4 Percentile:23.57(Physics, Applied)

Journal Articles

Magnetic and superconducting properties of CeTX$$_3$$ (T:transition metal and X:Si and Ge) with non-centrosymmetric crystal structure

Kawai, Tomoya*; Muranaka, Hiroshi*; M$'e$asson, M.-A.*; Shimoda, Tetsuya*; Doi, Yusuke*; Matsuda, Tatsuma; Haga, Yoshinori; Knebel, G.*; Lapertot, G.*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 77(6), p.064716_1 - 064716_9, 2008/06

 Times Cited Count:60 Percentile:89.2(Physics, Multidisciplinary)

Physical properties of cerium compounds CeTX$$_3$$ were studied on single crystals. Electrical resistivity, magnetization as well as their pressure dependence revealed that the antiferromagnetism of CeCoGe$$_3$$ is destroyed under hydrostatic pressure above 5.4 GPa and the superconductivity appears above this pressure.

Oral presentation

NMR study of single crystal YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Matsuda, Tatsuma; Haga, Yoshinori; Lapertot, G.*; Aoki, Dai*; Flouquet, J.*; Brison, J. P.*

no journal, , 

NMR study of single crystal YbRh$$_2$$Si$$_2$$ are performed. A high quality single crystal of 52% $$^{29}$$Si enriched sample is made. Owing to this enrichment, S/N is improved 100 times. spin-lattice relaxation, spin-spin relaxation and Knight shift have been determined as a function of T and direction of magnetic field of 7.2T. Below 6K, the Fermi-liquid behavior has been observed for H//a which is consistent with the previous data be Ishida et al. Behavior for H//c is quite different comparing with that for H//a.

Oral presentation

NMR study of single crystal YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Matsuda, Tatsuma; Haga, Yoshinori; Lapertot, G.*; Aoki, Dai*; Flouquet, J.*; Brison, J. P.*

no journal, , 

We have made 52% $$^{29}$$Si isotope enriched high quality single crystal sample of YbRh$$_2$$Si$$_2$$. Since the natural abundance of $$^{29}$$Si is only 4%, we can improve S/N of NMR signal by 100 times using this enriched sample. Spin-lattice relaxation time T$$_1$$ is measured. In this compound, the QCP is appeared at 0.66T for H//c, 0.06T for H//a. At first, measurements are performed at 7.2T in the Fermi-liquid state. A crossover to the Fermi-liquid state is observed below 6K for H//a as previous report. The behavior for H//c is different.

Oral presentation

Bulk electronic state of YbRh$$_2$$Si$$_2$$ studied by soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma; Haga, Yoshinori; et al.

no journal, , 

In recent years, YbRh$$_2$$Si$$_2$$ has been attracted much attention because it can be turned through a quantum critical point (QCP) by various small changes of control parameters. There are many angle-resolved photoemission spectroscopy (ARPES) studies for YbRh$$_2$$Si$$_2$$ by using low-energy incident photons to understand the nature of the QCP. However, large surface contributions were observed in their spectra, and its bulk electronic structure has not been understood experimentally. We have performed the soft X-ray ARPES for YbRh$$_2$$Si$$_2$$ to obtain its bulk valence-band structure. Obtained valence-band structure is similar to the calculated result of LuRh$$_2$$Si$$_2$$ within a local-density approximation, while the Yb 4$$f$$ bands are observed near Fermi level and are hybridized with conduction bands.

Oral presentation

Valence band structure of YbRh$$_2$$Si$$_2$$ studied by soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma; Haga, Yoshinori; et al.

no journal, , 

In recent years, YbRh$$_2$$Si$$_2$$ has been attracted much attention because it can be turned through a quantum critical point (QCP) by various small changes of control parameters. Many studies on its electronic structure have been performed for this compound to understand the nature of the QCP, but its bulk electronic structure has not been understood. Experimental observations of the valence-band structure including Yb 4$$f$$ bands are needed to establish the theoretical model which describes the electronic structure of YbRh$$_2$$Si$$_2$$ correctly. We have performed the soft X-ray angle-resolved photoemission spectroscopy for YbRh$$_2$$Si$$_2$$ to obtain its bulk valence-band structure. Experimental valence-band structure is similar to the calculated result of LuRh$$_2$$Si$$_2$$ within a local-density approximation, while the Yb 4$$f$$ bands are observed near Fermi level.

Oral presentation

Soft X-ray angle-resolved photoemission spectra of YbRh$$_2$$Si$$_2$$

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma; Haga, Yoshinori; et al.

no journal, , 

no abstracts in English

Oral presentation

Effect of magnetic field on magnetic excitation in heavy-fermion superconductors probed via neutron scattering

Kaneko, Koji; Raymond, S.*; Hiess, A.*; F${aa}$k, B.*; Steffens, P.*; Lapertot, G.*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

Oral presentation

Electronic structure of Yb-based compounds studied by soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Sekiyama, Akira*; Settai, Rikio*; Lapertot, G.*; Knebel, G.*; et al.

no journal, , 

33 (Records 1-20 displayed on this page)