Chandreyee Ganguli - Academia.edu (original) (raw)

Papers by Chandreyee Ganguli

Scientific Reports, Sep 15, 2017

The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeA... more The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeAsO 0.6 F 0.12 , an 1111-type iron based superconductor close to optimal doped region, has been investigated by measuring the temperature dependence of resistivity. Initially, the superconducting transition temperature (T c) is observed to increase slowly by about 1 K as pressure (P) increases from 0 to 1.3 GPa. With further increase in pressure above 1.3 GPa, T c decreases at the rate of ~1.5 K/GPa. The normal-state resistivity decreases monotonically up to 8 GPa. We have also measured the pressure dependence of magnetization (M) on the same piece of PrFeAsO 0.6 F 0.12 sample up to 1.1 GPa and observed T c as well as the size of the Meissner signal to increase with pressure in this low-pressure region. In contrast, for an over-doped PrFeAsO 0.6 F 0.14 sample, magnetization measurements up to 1.06 GPa show that both T c and the Meissner signal decrease with pressure. The present study clearly reveals two distinct regions in the dome-shaped (T c-P) phase diagram of PrFeAsO 0.6 F 0.12. The discovery of superconductivity in iron-based compound LaFeAsO 1−x F x with high transition temperature, T c ~ 26 K, has created a renewed interest in the field of superconductivity 1. By replacing La with rare-earth elements (Ln) of smaller ionic size such as Ce, Pr, Nd, Sm and Gd, a new family of high-T c superconductors emerges with transition temperature in the range of 26-55 K 2,3. This behavior is very different from that observed in cuprate superconductors where T c is found to be insensitive to ionic radius of the rare-earth ion. In pnictide compounds, the iron-pnictide (Fe-Pn) layer consisting of edge-sharing FePn 4 tetrahedron is responsible for the occurrence of superconductivity and a strong correlation between the crystal structure and superconductivity is observed 4-6. In LnFeAsO (1111-type) superconductors, T c reaches maximum when FeAs 4 forms a regular tetrahedron, i.e., the As-Fe-As bond angle is close to 109.5°4 ,6. It has been suggested that the pnictogen height h Pn measured from the Fe plane plays a crucial role for the T c enhancement 6. The pnictogen height is observed to increase and the FeAs 4 tetrahedron tends towards regular shape as Ln changes from La to Gd and it acts as a switch between high-T c state with nodeless paring and low-T c state with nodal paring 6. The effect of chemical pressure as well as external pressure on lattice structure and hence on superconductivity has been studied extensively to disentangle the relative contribution of various factors such as bond lengths, tetrahedral angle, and pnictogen height that affect superconductivity and provide valuable information to elucidate the mechanism of superconductivity in pnictides 4-12. Unlike chemical substitution, pressure is a continuously tunable thermodynamic parameter which can be used to understand the phase transition as well as charge conduction mechanism without introducing disorder in the system. There are several reports on the effect of pressure on superconductivity in pnictides 5,11-27. However, the effect of pressure on T c in LnFeAsO 1−x F x , in particular, in the low-pressure region, has not been unambiguously settled, possibly due to the sample quality and non-hydrostatic nature of the applied pressure. Also, the dependence of T c on pressure is quite sensitive to doping level. In the low-pressure region, T c shows an enhancement or suppression for 1111-type compound depending on the doping level and Ln ions 11-23. In pressure dependent ρ(T)

Journal of Alloys and Compounds, 1994

Abstract The electrical resistivity p ( T ) of the heavy fermion compound CeAl 3 has been measure... more Abstract The electrical resistivity p ( T ) of the heavy fermion compound CeAl 3 has been measured under high pressure up to 1.5 GPa in order to clarify the volume dependence of the electronic state in the heavy fermion. It is found that the temperature showing a maximum in the p ( T ) curve increases with increasing pressure. Compressibility was also measured using the X-ray diffraction technique at high pressure. On the basis of the data, a quantitative analysis of the volume dependent energy scale is examined using a simple theoretical model.

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

日本物理学会講演概要集, Feb 29, 2008

Physical Review Letters, 2011

We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which ex... more We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc=7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2)2+ polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling phonon in the occurrence of superconductivity in the hexagonal bronzes.

Journal of Applied Physics, 2010

... 8P. Sarkar and P. Mandal, Appl. Phys. Lett. 92, 052501 (2008). 9P. Sarkar, P. Mandal, AK Bera... more ... 8P. Sarkar and P. Mandal, Appl. Phys. Lett. 92, 052501 (2008). 9P. Sarkar, P. Mandal, AK Bera, SM Yusuf, LS Sharath Chandra, and V. Ganesan, Phys. Rev. B 78, 012415 (2008). 10L. Demkó, I. Kézsmárki, G. Mihály, N. Takeshita, Y. Tomioka, and Y. Tokura, Phys. Rev. Lett. ...

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

Materials Research Bulletin, 2013

ABSTRACT The pressure pressure dependence of the electrical resistivity of BaCo2As2 single crysta... more ABSTRACT The pressure pressure dependence of the electrical resistivity of BaCo2As2 single crystal as a function of temperature was measured at ambient and high pressures up to 8 GPa for the first time using cubic anvil high pressure cell. It is observed that at room temperature the resistivity monotonically decreases with increasing pressure and it remains in the metallic state even at an applied pressure of 8 GPa. From the temperature dependence of the resistivity measurements under pressure, we found that superconductivity is absent up to 8 GPa. The value of the electron's scattering factor (A) is found to be large at ambient pressure and it decreases with the application of pressure, indicating that the substantial electron correlation effect of BaCo2As2 is reduced under pressure, revealing a dramatic change of density of states at the Fermi energy.

Journal of Physics: Conference Series, 2010

... Phys. Lett. 92 182510 [3] Sarkar P, Mandal P, Bera AK, Yusuf SM, Sharath Chandra LS, and Gane... more ... Phys. Lett. 92 182510 [3] Sarkar P, Mandal P, Bera AK, Yusuf SM, Sharath Chandra LS, and Ganesan V 2008 Phys. Rev. B 78 012415 [4] Babushkina NA, Chistotina EA, Gorbenko O Yu, Kaul AR, Khomski DI, and Kugel KI 2003 Phys. Rev. ...

Submitted for the MAR11 Meeting of The American Physical Society Superconductivity at 7.7 K in ne... more Submitted for the MAR11 Meeting of The American Physical Society Superconductivity at 7.7 K in new hexagonal bronze HgxReO3 KENYA OHGUSHI, University of Tokyo, JST-TRIP, AYAKO YAMAMOTO, RIKEN, JST-TRIP, YOKO KIUCHI, CHANDREYEE GANGULI, University of Tokyo, KAZUYUKI MATSUBAYASHI, YOSHIYA UWATOKO, University of Tokyo, JST-TRIP, HIDENORI TAKAGI, RIKEN, University of Tokyo, JST-TRIP — We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc = 7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2) polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling ...

日本物理学会講演概要集, Aug 18, 2010

We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which ex... more We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc = 7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2)^2+ polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling phonon in the occurrence of superconductivity in the hexagonal bronzes.

Scientific Reports, Sep 15, 2017

The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeA... more The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeAsO 0.6 F 0.12 , an 1111-type iron based superconductor close to optimal doped region, has been investigated by measuring the temperature dependence of resistivity. Initially, the superconducting transition temperature (T c) is observed to increase slowly by about 1 K as pressure (P) increases from 0 to 1.3 GPa. With further increase in pressure above 1.3 GPa, T c decreases at the rate of ~1.5 K/GPa. The normal-state resistivity decreases monotonically up to 8 GPa. We have also measured the pressure dependence of magnetization (M) on the same piece of PrFeAsO 0.6 F 0.12 sample up to 1.1 GPa and observed T c as well as the size of the Meissner signal to increase with pressure in this low-pressure region. In contrast, for an over-doped PrFeAsO 0.6 F 0.14 sample, magnetization measurements up to 1.06 GPa show that both T c and the Meissner signal decrease with pressure. The present study clearly reveals two distinct regions in the dome-shaped (T c-P) phase diagram of PrFeAsO 0.6 F 0.12. The discovery of superconductivity in iron-based compound LaFeAsO 1−x F x with high transition temperature, T c ~ 26 K, has created a renewed interest in the field of superconductivity 1. By replacing La with rare-earth elements (Ln) of smaller ionic size such as Ce, Pr, Nd, Sm and Gd, a new family of high-T c superconductors emerges with transition temperature in the range of 26-55 K 2,3. This behavior is very different from that observed in cuprate superconductors where T c is found to be insensitive to ionic radius of the rare-earth ion. In pnictide compounds, the iron-pnictide (Fe-Pn) layer consisting of edge-sharing FePn 4 tetrahedron is responsible for the occurrence of superconductivity and a strong correlation between the crystal structure and superconductivity is observed 4-6. In LnFeAsO (1111-type) superconductors, T c reaches maximum when FeAs 4 forms a regular tetrahedron, i.e., the As-Fe-As bond angle is close to 109.5°4 ,6. It has been suggested that the pnictogen height h Pn measured from the Fe plane plays a crucial role for the T c enhancement 6. The pnictogen height is observed to increase and the FeAs 4 tetrahedron tends towards regular shape as Ln changes from La to Gd and it acts as a switch between high-T c state with nodeless paring and low-T c state with nodal paring 6. The effect of chemical pressure as well as external pressure on lattice structure and hence on superconductivity has been studied extensively to disentangle the relative contribution of various factors such as bond lengths, tetrahedral angle, and pnictogen height that affect superconductivity and provide valuable information to elucidate the mechanism of superconductivity in pnictides 4-12. Unlike chemical substitution, pressure is a continuously tunable thermodynamic parameter which can be used to understand the phase transition as well as charge conduction mechanism without introducing disorder in the system. There are several reports on the effect of pressure on superconductivity in pnictides 5,11-27. However, the effect of pressure on T c in LnFeAsO 1−x F x , in particular, in the low-pressure region, has not been unambiguously settled, possibly due to the sample quality and non-hydrostatic nature of the applied pressure. Also, the dependence of T c on pressure is quite sensitive to doping level. In the low-pressure region, T c shows an enhancement or suppression for 1111-type compound depending on the doping level and Ln ions 11-23. In pressure dependent ρ(T)

Journal of Alloys and Compounds, 1994

Abstract The electrical resistivity p ( T ) of the heavy fermion compound CeAl 3 has been measure... more Abstract The electrical resistivity p ( T ) of the heavy fermion compound CeAl 3 has been measured under high pressure up to 1.5 GPa in order to clarify the volume dependence of the electronic state in the heavy fermion. It is found that the temperature showing a maximum in the p ( T ) curve increases with increasing pressure. Compressibility was also measured using the X-ray diffraction technique at high pressure. On the basis of the data, a quantitative analysis of the volume dependent energy scale is examined using a simple theoretical model.

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

日本物理学会講演概要集, Feb 29, 2008

Physical Review Letters, 2011

We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which ex... more We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc=7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2)2+ polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling phonon in the occurrence of superconductivity in the hexagonal bronzes.

Journal of Applied Physics, 2010

... 8P. Sarkar and P. Mandal, Appl. Phys. Lett. 92, 052501 (2008). 9P. Sarkar, P. Mandal, AK Bera... more ... 8P. Sarkar and P. Mandal, Appl. Phys. Lett. 92, 052501 (2008). 9P. Sarkar, P. Mandal, AK Bera, SM Yusuf, LS Sharath Chandra, and V. Ganesan, Phys. Rev. B 78, 012415 (2008). 10L. Demkó, I. Kézsmárki, G. Mihály, N. Takeshita, Y. Tomioka, and Y. Tokura, Phys. Rev. Lett. ...

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

Materials Research Bulletin, 2013

ABSTRACT The pressure pressure dependence of the electrical resistivity of BaCo2As2 single crysta... more ABSTRACT The pressure pressure dependence of the electrical resistivity of BaCo2As2 single crystal as a function of temperature was measured at ambient and high pressures up to 8 GPa for the first time using cubic anvil high pressure cell. It is observed that at room temperature the resistivity monotonically decreases with increasing pressure and it remains in the metallic state even at an applied pressure of 8 GPa. From the temperature dependence of the resistivity measurements under pressure, we found that superconductivity is absent up to 8 GPa. The value of the electron's scattering factor (A) is found to be large at ambient pressure and it decreases with the application of pressure, indicating that the substantial electron correlation effect of BaCo2As2 is reduced under pressure, revealing a dramatic change of density of states at the Fermi energy.

Journal of Physics: Conference Series, 2010

... Phys. Lett. 92 182510 [3] Sarkar P, Mandal P, Bera AK, Yusuf SM, Sharath Chandra LS, and Gane... more ... Phys. Lett. 92 182510 [3] Sarkar P, Mandal P, Bera AK, Yusuf SM, Sharath Chandra LS, and Ganesan V 2008 Phys. Rev. B 78 012415 [4] Babushkina NA, Chistotina EA, Gorbenko O Yu, Kaul AR, Khomski DI, and Kugel KI 2003 Phys. Rev. ...

Submitted for the MAR11 Meeting of The American Physical Society Superconductivity at 7.7 K in ne... more Submitted for the MAR11 Meeting of The American Physical Society Superconductivity at 7.7 K in new hexagonal bronze HgxReO3 KENYA OHGUSHI, University of Tokyo, JST-TRIP, AYAKO YAMAMOTO, RIKEN, JST-TRIP, YOKO KIUCHI, CHANDREYEE GANGULI, University of Tokyo, KAZUYUKI MATSUBAYASHI, YOSHIYA UWATOKO, University of Tokyo, JST-TRIP, HIDENORI TAKAGI, RIKEN, University of Tokyo, JST-TRIP — We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc = 7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2) polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling ...

日本物理学会講演概要集, Aug 18, 2010

We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which ex... more We have successfully synthesized a new rhenium-based hexagonal bronze material, HgxReO3, which exhibits superconductivity with the transition temperature Tc = 7.7 K at ambient pressure and 11.1 K at 4 GPa. This compound is a superconductor with the highest Tc among hexagonal bronzes. Moreover, it presents the novel crystallographic feature that (Hg2)^2+ polycations, in contrast to monatomic cations in known hexagonal bronzes, are incorporated into open channels. There is evidence that conducting electrons tightly couple with Hg-related phonons. Our results inspire detailed studies on the role of the rattling phonon in the occurrence of superconductivity in the hexagonal bronzes.