(updated on 9/12/2014)

   

 

Table of Contents:

 

Research Activities

 

Group Members

 

Facilities

 

 

 

 

 

 

Members of the Strongly Correlated Electron Laboratory at CSU-Fresno (photo taken on 9/12/2014).  From left to right: Arnold Muradyan, Taylor McCullough-Hunter, Estaban Parades Aulestia, Shoji Hishida, and Dr. Pei-Chun Ho.

 

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Research Activities

 

What does "strong electron correlation" mean?


When the conduction electrons in the periodic crystalline structure of a simple metal, the interaction is so weak that they act like independent entities and move freely (ideal-gas-particle behavior, i.e., Fermi-Liquid Model).  But in the strongly correlated electron materials, which usually consist of transition metal or rare earth ions containing d- or f- electrons, the electron-electron interaction is so strong that the ideal-gas-particle behavior falls apart.  Sometime the strong interaction can modify the effective mass of a conduction electron to reach as high as 1000 times of a bare electron mass.

 

 

 

 

All instrumentation for measurement at the Strongly Correlated Electron Laboratory are designed and built by students under the guidance and assistance of Dr. Ho. 

 

   Student Presentations:

    

Banchong Somsanuk, poster presentation at 2012 APS March Meeting, Feb. 27-Mar. 2, Boston, Massachusetts, Abstract # S1.00303 (2012). Poster presentation title: Finite pulse relaxation calorimetry and specific heat of NdOs4Sb12, author list: B. Somsanuk, U. I. Urbina, P.-C. Ho, M. B. Maple, and T. Yanagisawa.

 

     

Pei-Chun Ho, Felipe Vargas, Ryan Fukuda, and Taylor McCullough at poster presentation of 2014 APS March Meeting, March 3-7, Denver, Colorado. 

 

 

 

Nick Soliz, oral presentation at 2011 Annual Meeting of the California-Nevada Section of the APS, November 11-12, SLAC National Accelerator Laboratory, Menlo Park, California, Abstract # F3.00007 (2011). Oral presentation title: Experimental Probe for Measurement of Thermodynamic Properties, author list: Nicholas Soliz, Ulises Urbina, and Pei-Chun Ho.

     

Ryan Fukuda, oral presentation at 2011 Annual Meeting of the California-Nevada Section of the APS, November 11-12, SLAC National Accelerator Laboratory, Menlo Park, California,Abstract # B3.00009 (2011). Oralpresentation title: Testing of a First Order AC Magnetic Susceptometer, author list: Ryan Fukuda, Smitha Sunny, and Pei-Chun Ho

 

Jussi Jose Amaral, poster presentation at 2011 APS March Meeting, Dallas, Texas, March 21-25, 2011. Poster presentation title: Synthesis and analysis of rare-earth nanoparticles Gd and Nd, author list: J. J. Amaral, C. Liang, D. G. Romero, P.-C. Ho, S. Attar, and D. Margosan.

 

     

Ulises Urbina, poster presentation at 2010 APS March Meeting, Portland, Colorado, March 15-19, 2010. Poster title: Instrumentation for measuring thermodynamic properties of rare-earth compounds, author list: U. I. Urbina, J. Thompson, and P.-C. Ho.

 

Johnathon Thomposn, 12-minute oral presentation at the 24th California State University Student Research Competition, CSU-San Jose, April 23 - May1, 2010. Oral presentation title: Constructing a multiplexer (scanner), author list: J. J. Thompson, advisor: P.-C. Ho.

     

Carmin Liang and Dulce Romero, poster presentation at Fresno State College of Science and Mathematics Annual Student Research Symposium, May 7, 2010. Poster title: Preparation and Analysis of Rare-Earth Nanoparticles (Gd and Nd), author list: D. Romero, C. Liang, P.-C. Ho, S. Attar, and D. Margosan

 

 

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Group Members

 

   Current

     Group Leader

           Pei-Chun Ho

        MS-Program Students

 

        Undergraduate Students

           Banchong Samsanuk, Physics-major, senior

           Hank Anderson, Physics major, junior

           Maya Castro De La Torre, Physics major, junior

           Ryan Fukuda, Physics major, junior

           Felipe Vargas, Physics major, junior

 

   Former

      Undergraduate students graduated from Dr. Ho's research group

           Carmin Liang, Biomedical Physics major, graduated in Summer, 2011

            Jonathon Thompson, Physics major, graduated in Spring, 2011

           Smitha Sunny, Biomedical Physics major, graduated in Spring, 2009

      Undergraduate students have ever taken Dr. Ho's Independent Study

           Daniel Ward, Physics-and-Chemistry major, sophomore

          Anna Tretyakov, Chemistry major senior

         MS-Program students graduated from Dr. Ho's research group

             Dulce G. Romero, Physics, graduated in summer, 2010

             Ulises Urbina, Physic, graduated in summer, 2010

         MS-Program students have ever taken Dr. Ho's Independent Study

            Emmanuel Angulo, 3rd-Year Physics MS-program student

            J. Jussi Amaral, currently attending UC Merced

             Kenia Velasco, Physics, graduated in Spring, 2010

            Jamie H. Vargas, Physics, graduated in Spring, 2009

 

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Facilities

   Plas Lab Controlled Atmosphere (Anaerobic) Chamber Model # 855-AC

         A new Plas Lab glove box is in the process of installation by the undergraduate student Ryan Fukuda.   (Thank to the support of NSF DMR-1104544)

 

 

   Ohaus Semi-Micro Balance

         A recently purchased Ohaus Discovery semi-microbalance Model # DV215CD has the capacity of 0-81g with the resolution of 0.01mg (81g-210 g, 0.1mg).  This balance enables us to weigh material accurately down to 0.01 mg.    (Thank to the support of NSF DMR-1104544)

 

 

 

   Cryocooler (zero magnetic field, 10K-fridge)

        An electrical resistivity probe mounted on a cryocooler


An APD HC-2 cryocooler has the capability to reach temperature as low as ~10 K.   Currently it has an electrical resistivity probe and a calorimeter setup.  The electrical resistivity probe and can monitor four samples for each run.  Thermopower, thermal conductivity probe, and 1st-order magnetic susceptometer to match this cryocooler are under construction now.

        A calorimeter for a cryocooler

 


 


Lab View program for performing the heat capacity measurements from 12K to 300K.  Top left graph displays the temperature history monitored by cryocooler’s thermometer and calorimeter’s thermometer during temperature regulation at each target temperature.  Top right graph shows the time dependence of the heat pulse input (red line) and the temperature of calorimeter (light blue dots).  After program performed a modified 1-tau relaxation fit (finite pulse width) of the whole trace, heat capacity can be determined.  The C (J/K) vs T is displayed in the bottom right graph.

        The 1st order AC Magnetic Susceptometer

 


The primary coil has 1964 windings, which can generate ~0.1 Oe AC magnetic field when ~100 microAmp is applied, and each of the secondary coils has 1133 windings.

        Original Design of a Thermopower puck

 


The thermal time constant of this original design is too long in the temperature range from 40 K to 300 K. Currently we are in the process of redesign a thermopower puck.

                      

    9-tesla superconducting magnet cryogenic system (1.6K-fridge)

         A 9 tesla 2” bore superconducting (SC) magnet 1.6 K refrigeration system (Janis Model 9TM-SVM-2-SV-HiEff-15V) arrived the CSU-Fresno campus in January, 2009.  This system will be setup for electrical resistivity, magnetic susceptibility, thermopower, thermal conductivity, and heat capacity measurements in the temperature range of 300 K and 1.6 K. 

 

Current status: All the hardware construction has been finished and it has passed all the tests in liquid helium environment.

 

Aluminum frame with vibration isolation to support the liquid helium dewar

  1.6K refrigerator and 9-tesla SC magnet on a transportation cart

  An electrical hoist and ceiling track with speed and brake controls for taking out the cryostat or the SC magnet and the magnet support.

Fix mounts in the room for the cryostat and magnet support with protection shields.

9 tesla superconducting magnet and the support structure on the mount.

 

4He gas handling system for the 1.6-K refrigerator

2-piece liquid helium transfer line purchased from CryoFab

 

    Home-built pumping stations

         * Diffusion Pumping Station: vacuum reaches ~ 5 X 10-6 torr.

 

 

         * Turbomolecular Pumping Station (model Seiko-Seikei STP 300): vacuum reaches ~ 5 X 10-8 torr.

 

 

    Refurbished 4He leak detector Varian 936-70

         Model 936-70 performs leak checking to the level of ~ 10-8 std. cc./sec.

 

 

    Home-built coil winder

         The home-built coil winder has controllable speed and is equipped with a precision wire tensioner (Fisher Baker Model 100 Dial-Tension, 30 AWG - 44 AWG).  It can be used to make small solenoids for pick up signal or producing small magnetic fields.

 

 

    Renovated high temperature box furnace

         A recently renovated Blue M model no. RG-2090A-3 1482 degree C box furnace, 120Volt, 1PH/50-60 Hz, 21 Amp, sample space 4"H x 4"W x 8"D.

 

 

 

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